What is the better way to dispose of old UPS?

If it can be repaired, you can repair it and sell it or keep it for your own use. If it cannot be repaired,check whether any of the components in it can be taken out and sold or reused. Otherwise use it as a stand, cover it with a cloth and keep flowers in it :-)

I would receommend you to service and fix the UPS and then resell it for a profitable price.

You should have done this before replacing!

if you remove the batteries call battery world and get a price on new batteries or just take the whole thing to a recycler they would accept it in one piece it is all metal so it can be recycled.

Or you can remove the old batteries in it and sell it for some price. After that use that box for some purposes without throwing it.(ex.Use it as a pot)