IMHO, I would sand the Jeep by hand for a few reasons. In my experience, when you sand down the vehicle, you will notice any flaws (dents, dings, depressions, ect.) that need to be repaired during the prep stage that may not be noticed if the Jeep is sandblasted.
Also, I have heard some "horror stories" of Jeeps that have been sandblasted, and it ended up "distorting the metal". I have heard that media blasting (walnut shells in particlular) worked well, and did not cause any warpage to the metal, but again, hand sanding would take more time, but would be worth the extra effort.
Whatever you decide, POST PICS! Good luck!
2005 Jeep Wrangler X (Black) / 1997 Jeep Wrangler SE (Red) / 2006 Dodge Charger R/T Daytona (Go Mango)