I have both, and have run both, singly and together.
The Helis are a neater, lighter solution to the problem, and give roughly twice the benefit and are slightly more money. If you are only looking for a minor tweak,(3/4") the GenMars work fine. I needed more. My wrists hurt just as bad with the GenMars as without. Not so with the Helis. Installation is easy on both. Not necessary to split the control module, but you can if you want.
If you need more than the Helis will give you, putting the GenMars under them works, but is much more complicated. Check the archives. There is a ton of info on this.
Chris Dolan has sat on my bike and he thinks that my bars with both are roughly comparable to his ZX12 stock, so we are definitely not talking cruiser riding position. I'm 5'11" and a tuck is no problem. Neither are 500 mile rides, or traffic jams, now.
[This message has been edited by SlowHand (edited 05 August 2000).]