Getting back to the original question, Bandai/Imai "originals" vs the newer Hasegawa offerings, if you're talking about "fighter mode" models - there is absolutely no comparison for one very good reason...
As far as "fighter mode" is concerned, in 1/72 the Hasegawa kits are
the only game in town.
If I recall correctly, Bandai/Imai never made the "pure" fighters in 1/72. Excluding the transformable versions which had all sorts of comprimises for "working" parts, the closest they came to making the "fighter" version was the "Super" version with the booster pods and add-on "FAST packs". This kit was based on the single seat
GERWALK configuration (I am using Macross terminology here -
pfft to the dumbed down Robotech version) and though the surface detail was very nice (recessed panel ines way back in the early 80's) the nose was entirely the wrong profile, resembling a droopy F15 nose. It could be filed/sanded to almost the correct profile, but one of the more radical solutions I recall for this problem involved sawing the nose off and inverting it. (true - this was published in a
Hobby Japan article)
Now, to the Hasegawa kit... I have three of these, though I haven't built any of them yet. These are comparable to any contemporary Hasegawa "modern jet" kit - surface detail is extremely fine and the mouldings are very clean and sharp. If you have read the reviews linked on the preceeding posts, you'll get the idea.