The 748 looks like a very sporting position, likely putting a lot of weight on the wrists around town.
The FZ1 has a very comfortable riding position, and a long engine service interval. Even though its 998cc, the FZ1 engine doesn't have a huge amount of pull below 5000rpm, but likely better than the 748. You probably won't get much above 7000 rpm in town on the FZ, which is where it takes off. The smaller engine of the 748 might mean you are working the gears more depending on how closely it is geared but that would be part of the fun. The FZ can do around 70 mph/110 kph in first gear, but you can also leave it in 3rd or 4th most of the time you are moving if you want. I think even a smaller bike is fun to ride, and if I were looking for an in-town bike I might consider something even smaller like the Kawasaki Er6n, one of the Monsters, or perhaps an R6 for track use.
I would expect the 748 to be better handling, and a better track bike, but many of the bike magazines said the FZ was a great all round bike, including track days, and continued to pick it best standard/street bike for a few years after 2001.
The FZ engine is mostly open to service, though you have to lift the tank to get to the top of the engine. You'll be taking apart the fairing on the 748. Getting the FZ1 re-jetted, with a better exhaust will add about 10 hp, but it really does not need this and the stock sound is good.
I don't know about the 748, but the Yamaha's dual lights both light up even on low beam (a pet peeve of mine if they don't).
Read as many road tests as you can find to get some better opinions on each bike.
