Aj, I see you are comparing the 2 barrel 273 to the 318. That's ok.
The 273-2 has .657 hp/cu in.
The 273-4 has .860 hp/cu in. where
the 318-2 has .723 per cu/in.
To all you big cube small block guys in this thread, I don't remember anyone saying the 273 was the best engine, the most powerful or any of the like. It does well for it's size and it's limits. Heck, there is no stopping with the comparisons until you get to maybe a 800 horse late model Hemi and there are many power plants larger and of course more powerful. The OP has a nice Dart with a 273 and wanted to know if he should keep the 273. There's always somebody out there that thinks bigger is the way to go. He just wants a street cruiser. He didn't ask how to build a top fueler.