Always go with the one that makes more putts.

To me the putter is a very personal thing and relates to how the putter looks to your eye and how it gets through the ball. With putters, I try a lot of different styles until I find something I like. This can also change from time to time as you go back and forth between putters. I prefer the mallet style putters and the Futura X Dual balance works great for me. I have not yet tried the Futura X5, but I would imagine I would like it as well. Spend some time rolling both putters and see which one seems more appealing and more accurate. Also, don't underestimate the importance of getting your putter fitted just like all of your other clubs. After going through a putter fitting with slow motion cameras and tweaking the loft and lie so the ball comes off the face perfectly, I am a true believer as you can see how much difference the correct fit makes. Good luck with your selection and either way you will be in good hands with your new Scotty.