I'm sure this has been resolved already, but I'll throw in my two cents for anyone else who stumbles onto this thread at any point.
I own both - 2000 4Runner Limited, bone stock other than the stereo, and a 2004 LX470, also bone stock. I do zero off-roading so my knowledge is limited to living with them as DD's - driving dynamics, reliability, amenities, etc.
Both are fantastic vehicles and you can't go wrong with either one.
The 100 series is HUGE, and it drives like it. Seriously, it drives like a boat. The 4Runner feels like a go-kart in comparison. In terms of driving dynamics the 4Runner is better, hands down. The LX has adjustable suspension settings, but that only goes so far.
As for build quality, as solid as the 4runners are, the 100 feels even more so. It's so well-built that I feel like it could survive a nuclear holocaust. Not to knock the 4Runner, but the 100 is built like a tank.
Interior space: 100 is bigger by a long shot. That's really all there is to say about that. I'm not a big guy and reaching to get something in the passenger seat or floorboard can be difficult at times. Easy to do in the 4Runner. 3 good-sized adults can fit in the back seat of the 100 relatively comfortably, plus you have that third row.
If ride quality is something you value, you want the 100. It is truly no contest between the two. Granted I haven't so much as even ridden in a TLC100, but the LX470 might be the smoothest-riding vehicle I've ever driven or ridden in. It's that plush. The 4Runner is jarring. I can't imagine the TLC100 ride quality being THAT much different than the Lexus.
The all-in-one navigation/climate control/stereo/everything else head unit in the 03+ (I think?) 100 series is a pain in the a$$. I much prefer the simpler setup in the 4Runner. The other disadvantage is that there is virtually no way to upgrade the head unit since there are so many functions controlled from it. You're stuck with the factory option and it's pretty expensive to replace, as I understand it. Some have figured out how to go aftermarket but it's a major, major, major undertaking and YMMV. The 100 series interior is definitely nicer than the 4Runner, but for the price difference that's to be expected.
If you think the gas mileage in the 4Runner sucks, drive a 100 series. You'll be begging for the 4Runner's fuel economy. I get about 14mpg and that's while driving with fuel economy in mind. Most people don't buy either vehicle for fuel economy, but it's something to consider. And the LX470 requires premium for some reason while the TLC doesn't...it's somewhere between a $55 and $70 fillup here in the midwest depending on gas prices. Larger fuel tank though, and it'll last a few days longer during fillups.
The 5VZ and the 2UZ are both great, reliable engines. Although the 2UZ is more powerful it's pulling around an extra 2,000-ish pounds so as far as acceleration, they feel about the same. The 2UZ is buuuuuuuttery smooth, whereas the 5VZ feels a bit more primal and not as refined. Despite less weight, it feels like the 5VZ has to work a bit harder at times.
As reliability goes, the members over at ih8mud (land cruiser forum) seem to have come to the consensus that the 4Runner is more reliable. This has not been my experience, but my 4Runner has higher mileage than my LX (219k vs 144k). 4Runner replacement parts are also less expensive. Nothing has gone wrong with the Lexus, but I haven't really had it long enough to have had something go wrong. Fuel pump in the 4Runner went out at about 210k, I'm having some sort of lingering brake issue, and I have a small oil leak somewhere. Other than that it's been great.
All in all, as I stated above, you really can't go wrong with either one but if pressed I prefer the 100. Just my .02.
