I have very good experiences of the 3/4 power main I bought from Kemps last season. Some occasional snags from battens on my lazy jacks, but they were set up for a standard main and I have not changed them yet.
Sails currently at kemps for first year complimentary service and the addition of a deep reef. Would recommend you have a deep reef added as if you are going up from a standard this is a much bigger sail.
really I wanted to go with a fully battened main, but was put off by the prospect of expensive cars etc., hence the KEMP PowerMain sounded attractive. When I approached my local sailmaker for a comparative quote, raised questions about whether a 'power main' was the way to go (although it's possible he might not have had access to the right battens). However, I'm coming round to the conclusion that on my size of boat I may be able to go for a FB main without the expensive gear... see http://www.ybw.com/forums/showflat.php/Cat/0/Number/648291/an/0/page/0#648291
I dont think there's any right or wrong answer... i guess you wont ever really know which is best unless you try them all!