Chris,
Long story short...I would avoid having Toyota install the 1808 if you go with this unit. Mind you, I am no expert but I've researched the 1808 heavily. IT literally fits right in the factory slot and all the cables (except the diversity antenna) plug directly in the back. I'm talking literally 10 minutes max to swap them out (from what I've read). Only trick is your 4Runner will likely have a second antenna cable known as the diversity antenna. It basically boost the antenna strength. The 1808 does no use this cable and if you do not splice it into a power (or maybe the ground) cable...you'll have bad FM coverage and some do not have AM at all.
Ok, so maybe not a long story short. As for it sounding better than another headunit...I'd say no. It will sound a lot better than your factory and from everything I've heard...people love it. It's a very simple project you can easily do yourself and makes a big difference. However a new headunit is made to do so much more, especially if you want to add new speakers, an amp, subs, etc.
Simply put, if you do not want to replace the factory speakers and want a cheap but effective upgrade, go with the 1808. I've been told the IPOD controls are nice if not a bit slow and you can get an AUX or XM/Sirus adapter if you really want.
Me personally, I really struggled between the 1808 and a newer headunit and in the end I am going with a newer headunit. I just want more and the capability to expand later if I so choose. I hope this helps.
Clay