I think the Speed has notibly less kick than an IR3 running at 400psi from AIR. I found the cocker to have more kick than an IR3 because of what Paul stated (bag block slamming back and forth). However, it's not necassarily worse for the user, just a different feel....
You can also run the Speed in it's stock form as low as 200psi, with allegedly no shoot down etc Haven't tried it myself yet this low but will try it at training tomorrow.
When WDP release the volumiser set, the Speed should be able to go as low as 150psi, which is bringing it into the 'kickless' arena of the Matrix etc...
I don't think you will be disappointed with either. The really good thing in my opinion is that they are both British designed and made (well, the eblade part of the cocker anyway), so you'll be doing your bit for the economy either way