Sean,
The sonic differences between are subtle, but they are there. The main difference is in the mids - the LG5 is a little on the sweeter side, and the RA5 has just a touch more bite. My sense is that the you might not notice the differences so much if you play live, especially if you are in a PA mix. In that case you might want to go with the bass that has the neck that you prefer (maple vs. rosewood).
You should also consider the music that you play. The LG5 will give you a slightly mellower thumpy tone, as opposed the slightly more detailed sound of the RA5. If you slap a lot you might prefer the RA5. Don't get me wrong though - the LG5 is a great bass to slap too, the RA5 is just a tad better for that (at least for me).
For what I'm doing, the RA5 is an ideal bass. It covers a lot of different styles well, and I like the slight brightness of the maple neck in live playing. I have a KBP5 on order and when it arrives I feel comfortable that it and my RA5 will cover pretty much any situation rather nicely. However, I've been lucky enough to spend a good amount of time with Mitch's LG5 and to be fair I would certainly not have been disappointed had I gone that route. Both the LG5 and RA5 sound sensational, and the feel of both is beyond belief.
To summarize:
1. If you want a slightly fatter, sweeter, more old school sound, or simply prefer a rosewood neck, go with the LG5.
2. If you want a slightly more aggressive, detailed, modern sound, or prefer a maple neck, go with the RA5.
3. Either of these is a wicked instrument and it is hard to imagine that you wouldn't dig both. Truly world class instruments, with tremendous consistency from bass to bass. Also, consider Jimmy's advice carefully (whatever it was), he has a knack for being right, and I was very grateful for his input when I bought my first AC.
What I was saying 
. and i am shipping it to a friend who will bring it over to me in Israel.
