Which Type To Get
A 500 series Citation or a LJ-JET. The others folks are right those are the ones to choose from. As far as which one is easier, the Citation, easier to fly and simpler systems. I've instructed in both (LJ as a 135 instructor pilot) and the Ultra and XL as a Sim instructor (also some aircraft instruction in the Ultra).
Early 20 series Lears are going to be gone with in a couple of years, not so much b/c of RVSM (most early Citation and LJ 35/36's aren't RVSM either) but because of noise complience. The 20's are stage II aircraft (VERY LOUD turbo jets

) and I think the early straight 500 Citation were maybe Stage II even though they were turbo fans.
Either way both type are usful. You might find it easier to find a Citation job, generaly the insurance requirments only require Simulator training. Also choose a Sim carfully, not all Sims can get you a type. In level C sims you have to do a 85/15 ride. 85% in the sim and 15% in the airplane (all the T/O and landings).
Good luck