I found them all equally enjoyable in their own ways and in regards to the world size, do not care overly about the world size as long as I have a blast playing in it (which I did in all 3). Sure some elements have been streamlined and its an RPG lite, but most the key stuff that made FO3 / NV great is still there.
With that said, reason I suggested FO4 as I mentioned was the gunplay is much improved over FO3 / NV and OP mentioned they did not like the VATS system.