[XPERIA X1 General] apprentice:
I am fortunate to actually own both these devices at the moment (thanks to an upgrade on my contract) so I can tell you what my findings are:

:: Hardware X1 problems ::

My battery cover refused to stay on. I was forced to get a small screwdriver and push the little metal tabs (near the SE logo) down a bit lower. This has been noted in other forums. The battery cover is a pain to get off if you don't have long fingernails.

The soft-reset button is under the said battery cover! I mean who decided that was a good idea??

The speaker is situated in a place that is often covered up by the palm of your hand (if you are right handed) and subsequently blocks the sound. The same can be said for the positioning of the camera lens, which frequently gets covered by fingers as you hold the phone in a natural camera position.

Notification LED's that are just too dim to see as they are located in between the keyboard and top panel. They have a rather confusing display of colours and none of them give you signal/bluetooth status for example.

There is a much documented report of a potential problem with case cracking.

No G-Sensor and the keyboard lacks the tactile feel and separate number keys of the Touch Pro.

But...

It has a fantastic screen response, very smooth. Fast landscape rotation on opening the keyboard, which glides out in a smooth curve. Dedicated hardware buttons and a cool optical sensor which works really well in web pages. GPS is really fast and accurate. A proper separate headphone socket.

:: Hardware TouchPro Problems ::

Unpredictable button presses

Lack of hardware buttons, especially a windows key and an OK key (also missing from the keyboard) No camera button, this is a serious omission.

Screen is not very scratch resistant (2 on mine caused by the useless case that is supplied) It's also very unresponsive, I find myself 'jabbing' the stylus at it sometimes to get it to acknowledge a response.

Poor battery life. Heavy/Bulky.

But...

has a beautiful VGA screen, the BEST keyboard I ever used on a mobile device, has a G-Sensor, a magnetic stylus which turns on the device on removal, touch sensitive D-Pad (Ok can be hit and miss sometimes but great for zooming) and has TV out.

:: Software X1 ::

The panels are disappointing. You can only set up 9 at a time, so if this really takes off you're going to have to sacrifice a few of your favourites. That's assuming that the panel idea is not going to turn out to be a flash in the pan. The ones supplied are a tad dull.

No YouTube application

Not all software works with the WVGA screen. Especially games. I found about 20 of my favourite apps weren't supported. Ok, this may change when developers bring out new releases but some may never work.

:: Software TouchPro ::

TouchFlo 3D looks sexy, but it is probably the biggest cause of crashes. I found myself constantly soft-resetting. Eventually after reading other users comments, I turned it off and a lot of problems disappeared.

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In conclusion....

Obviously pros and cons with both. I think none of us will ever be satisfied with everything. What aggravates me is that HTC (who make both devices) don't seem to take all the good stuff from past models and make the perfect device! You get used to one feature only to find it missing the next time you upgrade.

So we have to see which feature is important to us and decide.

Here is the clincher....

The TouchPro / FUZE is probably the MOST UNRELIABLE PDA I have ever owned. I constantly have to reset and cope with weird behaviour on a daily (no hourly) basis. Very unstable.

The X1 is probably the most RELIABLE PDA I have ever owned!!!! and has coped with a mountain of stuff I have loaded on to it, and it continues to cope admirably! I don't have to worry about using it.

This is the most important feature for me and is why ultimately I am selling the TouchPro very shortly.

Hope this helps you decide.