Bigger doesn't necessarily mean better when it comes to technology, but also I wouldn't really look at STO as a "realistic" portrayal of what these ships would really be like in-universe in 2409.

But personally I think the STO version of the soverign is far too small. It just doesn't look right. If you look at something like this: http://www.st-minutiae.com/misc/comp...son_medium.png it looks heftier compared to the Galaxy there than it does in STO.