All my comments below are based on ownership experience and seeing firsthand how a
suit handles crashes (which we see a lot of in our local race series.

). These comments are not about comfort, fit, features or anything else, just crash protection and survivability.
The top of the range Dainese, esp. the Ducati stuff is okay and will generally hold up for a few crashes. The lower range Dainese is crap- will fall apart at even the smallest fall. I've seen this time and again, especially when the newer guys (myself included) turn up with what they think are the best suits and then find out they aren't.
The Alpinestars are pretty mediocre and actually the worst suit I have ever seen is the top of the range GP replica (like what Michael Jordan was wearing when he rode the Desmosedici at a 2004 GP). Two of my buddies sprung the cash for them and they literally fell apart at the first fall. Some areas you expect suits to be a little weak like on the chest area when they are perforated. But not on the knees and elbows. The sad thing about the GP replica was that the crashes happened in the rain where the speeds were lower and there is less friction on the suit thanks to surface lubrication on the tarmac. I'd hate to have seen what would have happened if they took a high speed tumble in the dry with them.
This really bothered me cause it is THE most comfortable, lightest, coolest and sexiest suit I have ever tried on- just don't crash in it.
I haven't seen enough examples of the Spyke to comment.
But the name that keeps coming back over and over again is RS Taichi. These things are built to last. One nutcase buddy of mine has had over 10 crashes in the same suit and the stitching is still intact. I have yet to see one tear. I'm not wild about their designs or the way they print the colour onto the suits but it does last and at least it won't bleed red dye over you when you get caught in the rain.