won't make any difference if you don't take care of it. air cooled's that are taken care of can last 2000 hrs easily. Many last twice as long if taken care of. Liquid cooled's probably last a bit longer, i don't know any numbers on them sorry. If you can afford it get the liquid cooled. Friend has a 27 LQ on his Lazer and loves it!
It's probably a wash. The longer life of the LC has to be balanced against the higher cost plus time value of the higher investment.
LC's also are a little more complex, and perhaps prone to damage of their cooling system. How much does an A/C replacement engine of that size cost? Is this a mower that will be piling on high hours? Or will you want to replace it before the engine dies anyway? I always have 2 or 3 mowers in use , so I never wear out an engine. I'm ready for a better unit with newer technology before that occurs. But if you're piling on the hours and it'll be worn out in 2 years, the LC might be a good choice. Hard to say for sure.