I bought a Sierra about 4 months ago. I'll tell you my reasoning for the choice.
The CUDA's only advantage in my research was: 1) range 2) speed - The speed and range are only viable if you're diving with a team of all CUDA's - otherwise you're always going to be limited by the smallest, slowest scooter on the team.
The Sierra has a much smaller form factor which makes it the preferred choice on boats, or for travel, or lugging down the beach or in heavy surf; another big requirement for me.
Another reason was that if I ever need the distance of a CUDA I can buy a DSS fury battery for my Sierra which will give it more range than a CUDA, in the small Sierra package. win/win with only a small cost differential between a CUDA and a DSS equipped Sierra.
Even a stock Sierra has very reasonable range. I've done several full doubles dives at Lobos, well outside the cove and back and still had juice left. Unless you're on the trigger constantly, which is not normally not the case, the Sierra is a great balance between cost/efficiency/size.
