ram is the available memory when you switch your phone on. this is where the operating system is loaded at the startup. everything else after is loaded onto ram from the phone memory and memory card. this helps the phone run faster. the system software decides how to allocate space onto ram as you're operating ur phone. think of it as a desk u work on while all ur paper work is stored in the desk compartment (the hardrive)
internal memory is the hardrive of the phone. this is where u can store or your data like music, videos etc. the memory card acts like an external hardrive.
the N82 has the same ram as the N95 8GB. (128MB)
the N95-1 and the N95-3 have all the same exact specs. the only difference is that the N95-3 is designed for the US networks.
well the most important things to look for is the processor, thats how many MHz it runs at. RAM is also quite important but depending on the processor, u can have 512MB ram and carry a slow brick. Take for example the N95-1 and the N82. both have the same processor but different ram and they can both still run the same applications easily even though the ram difference between them is 64MB. (besides, we don't even use that much in our everyday uses)
the good things about the N93 is the large keypad.
the battery life's better than the N95
has better camera optics (3x Optical Zoom
Carl Zeiss Camera Optics) but less camera resolution
I have to say, unfortunately the N93 is now an old phone compared to the other giants (N95, N82)
can't wait for n97 successor