I have both, and have used both as a "primary expo vehicle". Their strengths and weaknesses and charms are very different; apples and oranges. I agree that for most people, the 40 would not be an ideal daily driver or expo rig, but they are very fun and satisfying to drive, wheel, and overland nevertheless.
FWIW, here is my take on both, from personal experience. JMHO, YMMV, etc.
The FJ Cruiser is a great compromise of modern comfort & convenience, safety, highway manners, and off-road capability. Sure there are other vehicles that do any one of these things much better, but the FJC does them all very credibly well and with Toyota reliability. Whatever you think of the styling, the name, or anything else about it, there are not many (if any) new vehicles sold at this price point that do all of these together as well as a bone-stock FJC. That you can drive across the country at 80 mph+ in perfect comfort, and still have such a capable off-road vehicle once you get there. Maybe a new 4Runner - I don't know what the going price of a 4R is, but as has been said, they are similar platforms anyway. A new Land Cruiser (and lots of other trucks) would do all this too, but for twice the price. Like I said, the FJC is a compromise but a very good one in all respects, especially for the price. As with most off-road platforms, the aftermarket can make it even better.
The FJ40 on the other hand, is a 30-40-year-old truck, designed before the interstate highway system was built, in a time when few cars had air conditioners and seat belts were an option. The fun in driving a 40 (or a Series Land Rover, a Defender, a Bronco, a Scout, a jeep CJ, or any other old car or motorcycle) is to appreciate it for what it is, not what it is not (compared to modern vehicles). You can't be in a hurry to get anywhere, and you have to be willing to put up with the leaf-spring ride, the lack of power steering and A/C, and you can't take a ton of equipment with you - but if you are willing to accept these limitations and enjoy it for what it is, there is nothing more fun to drive or wheel. Sure, you can modify the crap out of it to have all modern conveniences including coil springs and a big V8, but then you don't really have a classic Land Cruiser anymore, you have something else.
To me, it is pointless to try and build a modern version of a 40, or a Defender, etc. To do so completely misses the point - that these old trucks are elemental, purpose-built off-road trucks that couldn't be sold today, mostly because the market for them would be miniscule and hence unprofitable. Any styling or naming conventions for new trucks borrowed from the old ones are just marketing hype for the masses.
