I can't say which to avoid but as suggested check out triktalk.com. All makes and models are covered as to both trike manufactures and bikes themselves.
In my experince with the Yamaha RSV trikes Tri-Wing and Hannigan are your only choices. Having had both I prefer the Hannigan due to smoother, more stable ride due to it being wider and lower with independent suspension opposed to Tri-Wings solid axle setup.
On the Wings I've seen good reports about Roadsmith, CSC, Motor Trike, & Hannigan.
I would suggest your friend do a lot of reading & researching of the various companies. Also the installer needs to be checked out as some are better than others.
Larry