I have no idea how the wheels don't break, but mine haven't (Swiss Army brand) after six years of regular use. Re: size, for a two-week trip I usually pack a lot and/or try to leave room for anything I buy while traveling. Go bigger unless it's going to cost you more in checked bag fees for some reason.
I did have the wheels of one spinner break, but that was because I was lugging it all over Europe. We have another spinner that has lasted through at least three years of travel.
If you are checking your bag I don't think it matters if the suitcase is 25 or 29inches. Personally, i prefer lugging as small of a bag as possible.
Spinner wheels are great and so far no problems with them. I'd get the 25" since the larger one tends to be cumbersome and harder to cram in the trunk with all the other luggage.
The problem with a 29" bag is that you can easily pack it over 50 lbs. My 25" bag well packed pretty much weighs under 50 lbs, and if I expand it, it goes over.
If you are not flying, this isn't an issue....but you still have to haul the bag.