I have an older Kobo Aura and a Paperwhite 3. I've helped my neighbors with their Kobo HDs so I have a little more up-to-date experience with Kobos than from my older one. I prefer the Kindle but the truth is they're both really good. A coin toss is a good way to decide.
I don't do much with collections so I can't help much with that.
I think the problem you're going to run into with this question is all the Kobo fans are going to give you excellent reasons to get a Kobo and all the Kindle fans are going to give you excellent reasons to get Kindles. I doubt any of us are going to really be all that helpful.
My suggestion is to do some research on both, watch Youtube reviews of both and comparison videos, and then come in here and ask any specific questions you might have. Then you'll have some real information to use for a decision.
None of us knows what you'll like best. Except in rare moments of clarity none of us realizes that and we each know which one you'll like best.
Barry