Re: Nebula vs. Galaxy
I think its better to compare them to the Russian Kirov and Slava class cruisers of the Sovjet Union, the first one put the latest tech inside the largest and most expensive nuclear powered hull, the other one put well known tech into a a smaller conventional hull to have a backup if Kirov would fail.
So the Galaxy class puts the (b)leading edge stuff in the best possible hull and the Nebula is a really large but more conventional design.
"Sword is personal, brings slicing to a man, you getta that personal feedback, nuclear weapons?.. Meh, goes off big bang and you don't get any feeling.."