I have sailed a C36 MKII and own a 351 Oceanis. There sailing characteristics are different. The Bene sails more like the Late 80's to current Hunters where Douglas's Cats sail more like a traditional laid over, handrail in the water type. FUN! The "Euro" boats tend to sail more tender but corner and carve like a euro car. The Beneteau should be faster in similar winds. Catalina draws more of it's power from the Genoa where the Beneteau 361 draws more on the main. This should indicate the Catalina would weather up (turn up into the wind it the sails are not balanced) but I never experienced that with them, on the other hand the Hunters were designed to do this to keep most sailors safe if the winds kicked up. Mast height is about the same between both but you'll find with a bigger main and lighter keel your gonna wanna reef the main sooner on the Bene.
Generally you'll find they both sail similarly. The Bene has a lighter feel to it and the ballast is about 2k lbs lighter too. This means the tender feeling will be more pronounced. Beneteau will use the hulls width to push her back against the heel where Catalina's will accept the heel and use the weight of the keel. Catalinas get into a "groove" when heeled over to just put the hull windows near the water line. The Bene, Hunter, Jene's all sail on their feet very well and just as fast. That being said, you can sail a Bene just like you'd sail a Catalina or heavy keeled boat (heeled way over) but that is energy being wasted.
Iron Vs. Lead... I've had and sailed with both and of course ran aground with both. The lead keeled Catalina and Helms had suffered damage to the keel that was repaired with heat and a lead stick and iron blade to smooth it. But it meant it was hauled for a week. The cast iron keels on the Hunters are epoxied to the keel stub and bolted to the grid liner but in the bene they are sealed to the hull and bolted through to the grid matrix. Run aground in these and you'll flex the hull to take the energy out but your not going to be looking for a lead certified repair specialist. As long as the keels look good and are not "Smiling" at you on your short haul you won't notice or care. They both require maintenance each year with paint. Chances are both are probably barrier coated.
Another trait with the Catalinas is leaking chain plates, stanchions and handrails. The survey will tell the truth but I've never seen a Catalina that didn't leak. But then, all boats leak. If our homes had as many holes and attachments to their roofs they'd leak too.
)