IMO it's a choice between your personal preferences; if you're an iPhone person then go with the iPhone -- otherwise the android device. The most DISSATISFIED users are those making a change after years of usage on the other vender.
OnePlus 7T Pro is pushing a sharper QuadHD display with a refresh rate of 90Hz it doesn't manage to beat the apple 11 in terms of battery endurance. The apple11 has the advantage of a more optimized OS and a 720p LCD display that helps it go further.
It is difficult to compare these two, because they are on a league of their own. You might like the Quad display system on the OnePlus 7T Pro, but I think the OS and display performance on 11 are much better than the former. At the end of the day, it is your personal preference that matters!
Are you an Apple person? If so, go for 11. If you are used to Android and looking for an upgrade, then go with the 7T Pro.