Can someone help me understand why these 2015 lexus rx 350 SUVs have different front bumpers? I can't find anything online explaining why they are different. Same model supposedly, but different front bumpers? What is the longer (2nd pic) one called? Can the shorter one (1st pic) be replaced with the longer one? I'd really like to get the longer one put on. Thanks!

This is the normal bumper that I see.

This is a different front bumper that I see sometimes and I really like it.

 

your first picture is the base model, or could be called a sport design.
your second picture is the model with the designation of F sport.
search the forum, someone did a front end transplant of the F sport to a regular model. Fair bit of work, and a lot of parts required.
The base models come with a 6 speed transmission, F sport has an 8 speed transmission, and several other features, mostly cosmetic.
I think you are better off just looking for an F sport if you are convinced you really prefer the looks.