Which is easier timing belts or fork seals GL 1500

You will have to remove the fork to replace the seals. You will also need a fork seal driver. The spring is under slight pressure under the cap also. I always loosen the cap before I remove fork.
Not sure of your mechanical abilities either. It is harder than timing belts.
I can usually remove the forks easy after taking off front wheel. I NEVER take the fairing off to do fork seals. Make sure you TORQUE the fork pinch bolts when installing them. Do NOT guess at the torque value. Have seen some people think they are "tight" and the first hard bump says the were not.

For no apparent reason a fork seal had started to weep a little bit on my ride at the beginning of the season. Wipe it down ride around the block with a couple of hard stops and it would be back.

Took a piece of 35mm film negative and ran it down between seal and tube running it around the tube with the dust seal pushed up. It took 4 attempts with a ride around the block each time but it finally stopped and that was 1500 miles ago. Wrong time of year to be messing with the seals.

No looseness in my slider bushings and fork oil serviced at intervals. YMMV.

Do a search on fork seal cleaning.

Thank you DriverRider...that is some good advice. Will the thread detail how to use the 35mm film?

I agree that's it's the time of year to ride with minimal wrenching time if possible. So, I had some weeping on my right tube, forks fully serviced with new seals last March, so I tried buying a couple of SealMates (make sure you get the stiff yellow ones) and did as has been described with the 35mm film, and 1,000 miles later, tight as a tick! Heck, a pair of them is only about $11 delivered!

It's natural even with good seals for tiny pieces of dust and crud to work into seals now and then, and I'm not rebuilding my forks every time that happens. I'm sold on cleaning the seals before I bother replacing them. JMHO

Forks would have to come out and easier is a matter of following directions and comfort assuming you have the tools. I found belts to be quite easy, but they take a little while is all.
I did not want to mess with the forks as I do not have a mounted vise or anything. They were easy to remove (fairing stays on) and I had them completely rebuilt with all new seals/sliders/etc for about $100 for the pair. If you make an appointment you might be able to get them back from the shop the same day and do other stuff to it with the forks out of the way (oil? Coolant? Brakes? ...) .

I like the film cleaning thing and plan to try it. I wonder if there is anyone on this site who has to think about what 35mm film is... I am a hobby photographer so good there.