I use both, pros and cons. iPad is super convenient and opens a lot of creative possibilities, with a lot of great options. You can configure midi control from the OT as well, so you dont need to interact with the touch screen if you dont want to. You can get eventide, audio damage, mutable instruments, etc some top notch stuff.
I have a bunch of guitar pedals and I really like them too. If you get something like a strymon, theres a lot of thought and experience thats gone into it. Theres a bunch of really cool, unique and creative pedals out there, though you can probably replicate them to some extent though chaining fx on ipad, question is can you be bothered.
Pedals are just a lot more vibey to work with, you take what you get rather than wondering what you might be missing. For something like reverb and delay you can probably find something as an ipad auv3 fx, but if you want a particular type of distortion, or the stuff like the red panda particle, its going to be a lot easier to just get the pedal. Cons of pedals are cables, cost, usually mono and no midi, and limited recall ability.
To use the ipad you need an audio interface (and class compliant one should work), you’d go like OT cue outs -> audio interface ins -> aum -> fx -> interface outs -> OT ins. A plus of this is you can record the OT cue pre-fx as well if you’re not sure or just jamming. If you have 4 ins on the interface you can also record your jam, with OT main outs to the 2nd set of ins. If you tour you can back all your stuff up on the cloud and never have to worry about it.
I play guitar too, and I love pedals with that. I’m not sure I’d bother with pedals if I didnt, unless it was for something specific. Use AUv3 FX only in AUM I have never had issues with stability or reliability. I use my iPad for music a lot and on the whole I trust it, the only issues I’ve really had is with the older type of Inter App Audio and some specific bigger apps that were more complex daw like things.