The most reliable one is going to be the one that's the best sorted.
My experience is that Navajos are about the most reliable. They still break, but they are generally workhorses that I've been able to put a lot of hours on with minimal squawks.
The cabin class Twin Cessnas are better airplanes than the Navajos in a lot of ways, but they also have some significant design flaws in my opinion, most notably the fact that Cessna attached the turbo to the aircraft as opposed to the engine. It's a weight savings, but there are a lot of maintenance issues created by this arrangement.
Malibus... it depends on who you talk to. Some people have had good luck with theirs, some are always in the shop. As with any airplane, it depends on if you got a good one and how you maintain it.
Don't buy a P-Navajo. Also don't buy a Duke. Queen Airs I don't know much about, but they're old and not as much support.
Turbos add significantly to the maintenance. The exhaust gets expensive, the turbo systems are complicated (and expensive), and the engines work harder and thus break more. More heat = more breaking. Basically all cabin class piston aircraft are turbocharged, hence the extra maintenance.
Basically, you should expect $500/hr minimum for a cabin class piston aircraft. That's all-in expenses - hangar, MX, insurance, fuel, etc.
