I have the 12gallon Nano Cube DX which I think is pretty neat...(it all comes down to what lighting do you want, kind of filter, are you gonna have a sump, etc. etc.) If those are your two options - 12 g nano cube or 10 g scratch then I'd say the best one would be the 12 g nano cube.
Nano Cube:
Pro: A bigger tank (in gallons) is always better in a saltwater setup, more water=more stable reef...It comes with everything, and you get 3 compartments on the back (That's where you can hide your heater, pump to sump or a chiller). Stock lights are not bad, they are PC but they do the job. If you want to customize it there's alot of customization kits online (change the lighting or add a metal halide), If you really want to change the light you can always get rid of the top hood...plus the thing that I really like about the nano cube is the space inside on display...it's more of a square so I can have corals infront of the other adding to the effect of depth.
Con:That's it three compaartments, can't really fit a regular sized protein skimmer. You'll have to keep your hood open if you're running a fan, if you have a chiller will have to drill holes manually. stock PC lights aren't as strong as metal halide or T5's.
10 gallon tank:
Pro: more specific to your needs and wants. You can always get a good deal if you know what you want (i.e. lighting-T5, Metal Halid some come with fan). open top so wires and pipes go in and out easily without having to drill holes on the hood.
Con: Smaller tank. Since your corals and stuff will most likely be lined up left to right...it'll look like you have more and that you have a bigger tank but you kinda lose the depth effect. What you see is what you get, if no sump, heater is right there on the main display. no hood cover so some livestock can jump.
So to wrap it up...if you want an all around tank the nano cube would be better. Let's say you start of with FOWLR then decide to add some sps or things...it's very flexible...if you know you might keep sps or corals in the long run. However, If you know exactly what you want in the tank and that that's its main purpose (i.e FOWLR only, Reef only, etc.) then i guess the 10 gallon would be more cost effecient...not better, just cost effecient.