In some sense, these two are the same fighters, but its hard to guess Like cruiser received some overhaul. While keeping the overall design, the compartment with the main guns was shortened and re-designed, but pretty much its still the same ship like in ME1. Hard to guess.
Yes, one is more detailed Most likely they decided to remake them to be high-quality, as in ME1 the ship models were... In ME2 the models were made to be high-quality, and with the "return" of Alliance Navy they needed to remake cruiser and fighter as well. I know something similar somewhere already happened, but I cant remember where.