open heel fins: Cressi or Mares?

I'm in the market for some new fins, after completely wearing out my Tusa Liberators (which I never really liked much anyway). I've decided to stick with booties, and I'm considering a few options. I was hesitating between Cressi Spacefrog or Masterfrog, and Mares quattro excel. I'm a fan of the stiff blades, like Cressi makes, but what I'm concerned about is durability with heavy use (I dive year round, 6 days a week). Mares would be easier and cheaper to get hold of from where I'm located, but if Cressi is durable over time it might be worth it. Anyone got any thoughts on those options (or other ideas in that style)?

I'm very familiar with the Mares but have never used them. I too had the Liberators for quite a few years. Now I use the Cressi Rondine A fins. I think they are a bit stiffer than the other Cressi's. I really like them. I've used them in blue water, lakes, and rivers with significant current and they perform flawlessly, not requiring olympic strength to propel them. (I'm 53 and no Mark Spitz) They are fairly long, approx 25 inches. I've replaced the stock straps with springs. I believe they are available at Leisurepro for $65.00 or so.