[OnePlus 5 Accessories] djsubterrain:
Ultimate shield is the most similar to the official protector (sadly no longer available in the UK, I think it is still available in other countries like the US), it also inherits the problem of the frame overlapping on the display and you lose a border of the display, the quality however is very strong, it's thick, still responsive and will probably protect the best. Where it can fail is with case compatibility since it covers the full face of the phone going very close to the edge and actually ends where the phone starts to curve to the sides, don't even try using it with a Spigen case, it won't work with any of them since they wrap themselves so tightly onto the phone.

The Nilkin is pretty much compatible with any case since it doesn't go right to the edges and rather will only cover the front face of the phone up to where the display bends to meet the sides of the phone, unfortunately a lot of people don't like that, it also means that it can get a dust halo around the edges, wiping gently with a good alcohol wipe (I recommend Zeiss lens wipes) can take care of that. The placement of the protector also means it can quite easily catch on things, like the inside of your pocket for example, it should be possible to just press it back onto the display if no dust has gotten under it.

So, it depends on your usage case, if you don't use a case, have the phone naked or use a vinyl skin I would definitely recommend the Ultimate Shield for strength, protection and quality.

If you're using a case then go for the Nilkin as it should clash with any case out there.

There are, obviously, other protectors though, unfortunately, most of those are only adhered around the edge, I think they're probably all made in the same factories and then just branded differently because you always seem to get exactly the same wet/dry wipe pack with them, so, because they're only adhered around the edge, you will get the rainbow effect in the middle of the display as the protector isn't making contact with the actual display, this is why you get the "rainbow effect" and possibly lifting on the corners.

Both of these protectors have full face adhesion so you shouldn't get the rainbow effect or the problems inherent with those types of protector.

"Better" is a very subjective word, what you should say is "Which protector is best for ME".

One thing I would say about protectors is don't fall for the "Oleophobic" description, this means the protector should be quite resistant to skin oils, the reason why you get streaks and finger marks on your screen, however oleophobic they might say they are, there is no screen or protector yet produced which will get no streaks due to skin oil. Keeping a cloth will help but will really only spread the oil thinner and will still leave some kind of mark on the screen, the only way to properly remove them is to use alcohol wipes.

Another thing I would say is, if you want to use a case AND have a screen protector, usually the best solution would be a case which has the wallet style where there is a flap which goes over the display, that way, if you drop the phone then the casing will protect the sides and absorb some of the shock damage, the front cover, along with the protector should protect the display surface well. Those cases are usually a lot more compatible with screen protectors too since they don't usually wrap around the phone too much.

Also, when it comes to matching a case to your protector, the worst cases are usually the cases with two layers, the soft rubber TPU layer combined with a plastic shell, due to the rubber usually wrapping round the screen to provide protection for corner and face drops, unfortunately those are usually the most protective cases too.

To be honest, YouTube is probably your best friend when making decisions like this, there is pretty much a review for any case for any phone by reviewers who do this for a living and usually know what they're talking about and, in a lot of cases, can definitely affect the popularity and sales of these products. Just look for a review channel which has a good subscriber base since they usually have been doing it for longer and provide good information.

For our phones I would recommend the following :

Absolutely Savage : https://www.youtube.com/user/jonobradley123 (Good UK reviewer who mostly specialises in the OnePlus phones and has been a favourite with OnePlus owners on the forums for a while)

Big Unbox : https://www.youtube.com/channel/UCE639ItHrCPOsQ4rAfVIbuA (Excellent US reviewer who will meticulously test protectors with several cases he has for compatibility and must spend a fortune doing so, so he deserves a good following for this)

Both of those reviewers had the OnePlus 5 and, between them, managed to review pretty much all the available cases and protectors, usually testing them together to give a good idea of what you can expect.

For more general phone reviews my 2 favourite channels are :

Erica Griffin : https://www.youtube.com/channel/UCB2527zGV3A0Km_quJiUaeQ (Excellent technical reviewer who will test the phone's aesthetics, camera. performance, features, software, sound and display quality)

JerryRigEverything : https://www.youtube.com/channel/UCWFKCr40YwOZQx8FHU_ZqqQ (Excellent technical reviewer who tests each phone to destruction and has consistently recommended OnePlus phones for durability)

MKBHD (Marques Brownlee) is good also but, to be honest, technically, I don't rate him very highly compared to the reviewers above.

Hope all that helps your decision.