These models (1A5) were already old, and only used by heavy reconnaissance units when I was in the German army 32 years ago. The main tank brigades already had Leopard 2 back then. The main point of the Leopard 2 for Ukraine is that it has a longer range gun than the T-72 and whatever else Russia has, so that it can attack from a larger distance with relative safety. As far as I understand this is not the case for the Leopard 1. Probably better than nothing, though, and hopefully they'll still have better targeting electronics and night vision than their counterparts. Also, the Leopard 2 has more or less a standard NATO smoothbore gun, made by Rheinmetall, the same as the Abrams, and ammunition should be plentiful. That may be not be the case for the Leopard 1, which has a very different gun.