* Grizzly Bears - Some great backpacking places - the Winds, Alaska - have grizzly bears which require more discipline about food. In the Sierra, there are bears but no history of them eating people.
* Lightening - Not as likely to make you shit in your pants as the Rockies in Colorado or Wyoming.
* Water - Some great backpacking places - the Grand Canyon - you MUST get from point A to point B that day because you need that water at point B, there's no water along the route. Water sources are plentiful in the Sierra
* Where to camp - Some great backpacking places - the Grand Canyon, the Tetons - are tightly regulated by permit as to where you can camp each night, so you have to know your pace beforehand and then stick to the plan. The permit system in the Sierra is easier - you pretty much just say where you are entering and exiting
* People - if you are a novice, it's good to have other people around, not too many and not too few. There will be more or less the right number of people around in the Sierra
* Logistics - Getting to the trailheads from Bishop, CA, not so hard.
* Reward - So beautiful. You have long distance views. You aren't just in the trees.
* Lyme Disease, etc - Not so bad.