Get a survey so you can see what you may or may not have to dump into either of them to make sure they're reliable.
I'm not sure there is such a thing as a cheap sport boat, in the end.
The twins are nice if you're offshore and lose one of the motors, you can still get home.
The single makes DIY repair easier, as there should be a lot more room in the bilge for you to work on it.
I have had my Pantera for a few months now, and I almost regret getting the twins, for a few reasons:
*I have unlimited towing through boat US, so I'm not really that concerned about getting back to the marina if something breaks.
*My potential exposure to pricy repairs is doubled.
*There's not much room in the bilge to work on it... I'm going to have to hire a russian midget contortionist to change the spark plugs.