If you look at this video at around 23:45
A PBusardo Review - VZ VV Tube Mod (AKA Lavatube) Full vs. Mini - Vaping Zone - YouTube you can only go to 4.9v with a 2ohm coil on a full sized LT. 3ohm's gives you more adjustment.
I use 2.5ohm's myself and I'm happy with the range I get. Really what I was saying is you get a better range of voltage settings at 3ohm and with 4ohm you could use all the way up to 6v without hitting the limit. I think 2ohm is too low and the best range is 2.5-3ohm for the LT to put you in the best "real" adjustment range where most people would be happy.
Eventually I plan on running some tests of my own but I'm not sure how I'm going to go about it because I want it really accurate. I need to build a better extension to hook my multimeter up also. I also would have to build a few coils to test with..I have over 25' of NiChrome wire to do so. I might just build some "open coils" at different ohm's to test with..maybe with coils attached to screws. If I do this I will post my results here.
But no matter the tests I'm very happy with the range I get with 2.5ohm coils..if I was using the coils just on a LT I would probably use 3ohm as the atomizers that came with the kit seem to give me a good range also...