The Bullet coaxials and HLCD's (in 6.5") are direct bolt/screw in the roswell cans.
From my understanding, the wetsounds 650 coaxials require some shaving in the cans. However the new wetsound coaxials, rated at less power than the 650's, are a direct bolt/screw in.
I went Bullet due to looks and because they are rated for more power. Plus i didnt have to mod the cans at all. However, i didnt have wetsounds speakers i was trying to match like you do.
THe difference between the two quality wise is preference. Both are top of the line.