Use the more powerful amp and keep a check on the volume. You can tell if it is loud enough or too loud, trust your judgement.
There is less chance of the 1000w amp clipping and less chance of it packing in under sustained load. I'd test the whole system at gig level first for a good hour or so just to make sure. Don't leave it to the soundcheck. Make sure the new amp is fault free and robust way before hand. But have the other amp as a spare with you too. Ideally have a spare for everything.
Current Lash Up:
TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.