Well I have a Quigley so I'll give you my thoughts. I think Quigley leaves lots of room for improvement.
The front axle
- can't disconnect the sway bar without completely removing it.
- reuses factory shocks which look as if they will really limit suspension droop if the swaybar was removed.
- horrible turning radius - looks as if the front trackbar mount on the frame side needs to be moved up a little to gain more clearance with the pitman arm.
Rear axle
- reuses factory shocks (they actually weld on an attachment to the factory shock mounts) this i'm sure will limit the rear articulation. Not to mention I have to cut off the crap they welded on when I replace these with longer shocks.
Everything else
- quigley uses a transfer case from a ford superduty, should be plenty strong.
- the gas tank is shortened (mine is now a 29 gallon tank)
The sportsmobiles from what i have read have a much better turning radius, the atlas transfer case which allows for a lower low range, better articulation since they have swaybar disconnects and aftermarket shocks. I'm not sure if they all come with it or not but the 46 gallon transfer flow gas tank is at least an option, it might be included in the normal conversion. Sportsmobiles also come with spacers for the rear wheels so the front and rear track match which is nice, supposed to make for better handling.
Needless to say i'm glad I purchased my quigley but if i was buying new and had the extra $$ I'd go with the Sportsmobile conversion without a doubt. I'd kill for the better turning radius!
There's also some other conversion companies out there that are supposed to do nice work.
http://www.quadvan.com and
http://www.salemkroger.com/ are two that come to mind.
I'm gathering the Quigley info off of mine which is a 2004.