The AC 400 has been a very good guad for me. It was fine tell i rode a 500 and realized how underpowered the 400 is.
Thanks

 

My dad drives a 400 ac and I have a 500 ac manual. In 2wd my 500 steers nice. With the wide tires it's a little heavy at times depending on the surface. The 400 has the narrower front tires so it steers a little softer unless you're on the throttle too much and the diff is working hard. The 400 goes everywhere my 500 goes. That's not much of an issue. The 400 is a bit faster than my 500 but I have a winch, front rack basket and rear basket(i'm also 100 lbs heavier than my dad.) factor all that in and the 500 should win if you raced them stock. The 400 will pull a bunch but not as easily as my 500 will. The shift lever was a small factor in my decision to buy a 500. I thought I would be able to tell it(400 ac) was in 4wd too much but I've riden both quit a bit now and I can't tell the difference unless I push it. I'm actuall the only memeber of my family to get stuck because of the shift lever. I rode into a DEEP mud hole/pit, forgot to shift to 4wd before hand, and bogged down and stopped so bad that my dad ran smack into the back of me. We laughed all the way to the dealer to buy a new brake light. Moral of the story is the 400 is also idiot proof. I can't find a fault with the 400 being 4wd all the time.