I have owned the following three 4x4's .
Jeep Wrangler 2013( Very capable offroad, but week engine, couldn't climb to the top of extremely tall dunes, whereas a Land Crusier, or previous version of Nissan Patrol could do it easily.)
Nissan Pathfinder 2008, (Good Power, but capability is average, would hit the bottom due to low ground clearance, and 4x4 system is not that good.)
Ford Expedition 1998, ( Week engine, Good ground clearance in pre-2001 models, extremely capable 4x4 transmission and good low end torque, but cannot make up to heavy dunes due to engine power and huge size.)
I have heard good reviews about FJ, infact all Toyota 4x4's and Xterra.
Off-roading is all about skills , you can manage with an average 4x4's, if you know the basics right. I have seen locals doing great with little Suzuki Jimmnys and RAV 4s.
Your budget for 50K can fetch you pre 2009 models only, so it comes down to personal choice. If you know how to drive a manual may be you will get more options. But remember in such old vehicles chassis and transmission may have already taken lot of beating, better search for good condition one.