[Xperia Tablet Z Q&A, Help & Troubleshooting] Walter_White:
I abstained the vote cause the question does not bear a black and white / yes or no answer anymore these days.

In my humble opinion, and I picked up the smartphone / PDA / mobile device modding bug back about when this site catered to the the original HTC XDA almost exclusively, and Steve Jobs was merely having wet dreams about his iPhone (*1)... nodded RIMs have gotten to a state where they are overvalued. Saying a custom ROM is always way ahead of stock is like saying "one device with a fixed featureless fits everyone perfectly".

Custom ROMs had their deserved heyday when the industry loaded up near every carrier distributed smartphone with scrappy bloatware that made you weep. Depending on the mobile OS at any given time it was nigh impossible to get rid of that stuff, unless you flashed the whole shebang. From there on the custom ROM scene kinda exploded along with the market distribution of smartphones and later on tablets, certainly owed to the introduction of Android over older generation closed source systems, which enabled much more in-depth possibilities of adding novel features, fixing stuff that was basically broken out of the box and integrating all of this nicely.

(For a frame of reference: I tossed my PalmPilot and Nokia phone when the HTC Wallaby (Telekom MDA or so)hit the shelves... Early adopter by nature and I thought combining cellphones and PDAs, bother which I used avidly was the most revolutionary idea since the combustion engine. This was generation Windows Pocket PC, basically a PDA with cellphone feature thrown in as an afterthought (the antenna actually doubles a stylus compartment). Phone integration was a PITA on good days. On bad, long work days it might just happen that your moody battery would jump from 35% to flat out dead within a mere six minute phone call. Yet, no biggie right? Well, it was, the devices had no non volatile storage. Dead battery means go home, pray your last phone backup is recent enough and restore the entire thing. I spent a lot of time fixing this device (windows style - shoehorning in binary OS components from newer PocketPC versions and prodding the registry on the phone (!)...) to a point where it was almost usable as PDA only device, supplementing telephonly with a Nokia.

A while later better devices came out, PocketPc was scrapped for Windows Mobile and in high hopes I got a HTC Charmer. This looked like a more solid platform and indeed proper custom ROMa emerged, adding real functionality and allowing to get rid of carrier branded crap, later even RIMs emerged with Windows Mobile version updates never intended for that phone, some even taking the recent cutting edge HTC front-end, the first incarnation of Sense (I think it was called vanilla). I figured the really bad conceptual problems were fixed and merrily went along. But, as god hates my guts, I drained the battery accidentally, only to find that the phone would still go dead, deaf, dumb and wiped despite a good three or four years of technological progress. I was so confident that I neglected backups with that model and basically lost the majority of my stuff again. The Nokia dumbphone was back in the game, the HTC left a dent in the wall that required plaster and a patch of new wallpaper.

TL;DR: The first gen smartphones (PDA with cell module afterthought were such flawed concepts, badly integrated, that keeping recent backups and maintaining it operational took quite an effort on user side, on that sort of negated the higher productivity of using one altogether. But bear with me now, I am still circling around the point or two I want t. Make.

Because a few months after I abandoned smartphones for good (or so I thought) Apple coughed up their iPhone prototype and a few months later pumped it to market. I was amazed (not because of the technological feat, they were more or less throwing R&D money bricks at existing tech and concepts, however they exactly figured out what went wrong in the early generations, fixed that stuff, added fingerdriven multi-touch in favor of stylus driven displays and, this is the real kicker, in a time and age when the cool cell to have was a Nokia 8 Series or a decent, very small flipphone or clamshell they managed to brainwash their customers into what PDA and smartphone adopters at that time already knew - it's totally worth to dump the train of ever smaller telephony only cells for a much larger, more fragile device because of all the freedom and power those things offer you.

I kept my guard and obviously went for Android devices once I got back on the horse. HTC Desire, a backup Wildfire, Desire HD, Sensation, One S and a few tablets along the way. Now, here is the kicker. The Desire ran much better with a custom. The Wildfire could only be updated to a recent Android version with a custom ROM due to HTCs sometimes appalling quick update discontinuation. The Desire HD ran a basically stock custom ROM! But with lots of lovely icon eyecandy, so I stuck with that too. The Sensation benchmarked equally (give or take 5%) but the ROM added novel features, properly implemented, which I decided to stick with. But frankly, it was because I could. I would not have recommended a newbie to Android flashing to take the plunge. My current HTC One S has a recovery downloader and is rooted cause some essential apps I can't live without need it. Full custom ROM switch. I see no point. Android has come a long way. If today I have bloatware I can go to App Manager and disable them. Icon gone, runtime resource hogging gone. Many features that were the selling points for a custom ROM a while back are now natively incorporated.

This is just how I feel about my Sony SGP311 now. It runs 4.2.2 rooted, no recovery yet. This is planned, maybe at some point a stable, close to stock custom kernel to allow some overclocking on a per app basis for XBMC. But other than that it just Danny works. The Sony skin put over stock Androi. Is not that bad, and more to the point it never gave me the impression of hogging the system. Turn off what is useless to you, Office suite, walkway, etc and be on your merry way. It just comes down to what you do with the device, but as a custom ROM junkie who has just gotten off the habit, for me it makes no sense anymore.

Now, if you made it all the way here, I ran two benchmarks on my 4.2.2 root but stock. Maybe they aid you in your decision.

EDIT: the attachments are garbage. Here are proper links:

http://i.imgur.com/vMFEX1p.png

http://i.imgur.com/IEPVvMS.png

http://i.imgur.com/mB5MKSH.png

Also, none of the above is supposed to rain on the developers parade or something. I admire your skills and dedication over all those years, and there isn't a single custom ROM that went onto my devices withour a PayPal "crate of beer" donation ever. However, the fiddling, time spent reading up on custom ROM choice, issues and unlocking process etc is just not in relation for me anymore. Those thoughts are yours to reject, spindle, mutilate, adopt, oppose or plainly ignore... Just speaking for myself here.