Is this the result of the engine? does fallout 3 suffer with these issues as much?
Fallout 3, and New Vegas both use the same engine, so, yep. The problem persists with them. Granted, the engine was updated some for FO3, not sure if there were any changes between FO3, and NV though...... For what it's worth, FO3, and NV, both run better than Oblivion on my machine.
The main problem is the games rendering engine. It renders EVERYTHING in the direction you are looking, whether you can see it or not. So, looking across town, is really gonna thump on your performance. Another issue is AI, if you have a selection of actors loaded, (in your immediate vicinity, doesn't matter if you can see them or not...) that will bog down the cpu..... the game engine is really poorly optimized.