both tanks have a positive effect from where I am sitting.
The smaller tank really lets the engine show itself. I have seen them done using sportster tanks and its almost too much engine. but then again, engine is a bit like cleavage to me
I also really like the gas cap being round and centered on the tank. I am not a big fan of the rectangle gas cap of the original tank. One other positive aspect of the smaller tank is the placement of the seat. with the tanks physical size being smaller than that of the original tank you have more room to manuever and properly place the solo seat.
I am planning on keeping the original tank because the tank matches the lines of my bike. it really does flow right into the backbone of the bike. I am going to be going with a more sleek/technical/modern paint scheme with the bike and the rectangle gas cap actually fits with the scheme and design.
Ultimately its up to what you want to build. Pick a color scheme and take a step back, do some drinking, do some thinking or just dont do anything and it will come to you.
i like em both, cant go wrong with either in my opinion