Moat compact excavators usually have rubber tracks. Usually because compact excavators are used for landscaping work, therefore the tracks would not tear up and lawn, or soft soil. Any excavator over about 3 tons usually has metal tracks. They provide more traction when on gravel, but they tend to tear up lawns, and leave little notches in pavement/ashphalt. Saying which one I prefer would really depend on te type of excavator.
Maintence wise, rubber tracks hold up pretty good. They wear about the same as a tire would. After a couple of years of pretty steady use they can split, and the tread could start to wear. Some of the good things about them is that you dont have to worry about chains, and pins. Also the rollers will wear a lot less then on metal tracks. Plu in most cases it is a lot cheaper to replace a pair of rubber tracks, as opposed to rollers, chains, pads, and pins.
Metal tracks are better for rough terrain. Climbing hills, ledge work, and better when trying to get yourself out of tough situations. Some of the cons of metal are that they tend to fall off easier, they snap and bang while your driving, you have to worry about the pins coming loose, loosing pads, and the chains and rollers wearing out a lot faster. The good things about them is that they will outlast a pair of rubber tracks, give you better stabiliy and traction, and always be reliable when getting yourself up out of a hole.
Thats my argument on rubber vs. metal tracks. If you feel that I have missed anything, or there is anything that I am missing, feel free to comment ! Or email me at firstname.lastname@example.org
Thanks for reading !