OK, I have both. I absolutely love the twill and it makes my IPF feel scratchy in comparision. They are the softest diapers I have ever felt (even velour). BUT... Well, they are so soft and silky the serging can come sliding off at the ends, and I have one of the PFs sitting on my sewing machine since I am going to have to repair the end where there is a hole. So they are the best PFs ever, but they are not necessarily as durable as I or CPFs. TinyBirds knows this so she is trying to find a better supplier so she is not selling them anymore until she resolves the problem. It is only a problem in a few PFs, but she has excellent customer service and wants everything to be perfect. They might not be in stock until Spring of next year.
That being said the birdseye is really nice too. It absorbs more I think, and it is still soft. I think it is nicer than IPFs, but not necessarily softer. Just absorbs more and pinning it is like going through warm butter. So you will like them, but I don't know if it is worth the extra expense for the birdseye (except they are as absorbant as 2 premium CPFs in my opinion).
I have heard great things about Thirsties PFs, they are supposed to be softer than IPFs and they are cheap. www.babycottonbottoms.com
So I do love TinyBirds colorgrown PFs, and would buy more twill if they were in stock (even with the serging issues they are completely worth it), but I would not do a huge stash of the birdseye. It is less stretchy and not as soft (but still softer than CPFs). But it is easy to pin and a great night diaper. So you could get a few for nights and trips and also get some Thirsties for general use. Hope that helps!