Mitsubishi would be the logical choice.
In terms of durability, historicals over the last 15 or so years would show that the L200 engines have outlasted the others in class, including the Hilux. From my experience, the Hilux engine components tend to become problematic after just 3-5 years whereas the L200 engines that are now acting up at the models from around 2006-2008.
Maintenance and parts should be almost equivalent. With the L200 however, the only parts you should require within the first 10 years or so would be regular maintenance items like filter, brakes etc. With the Toyota, recent history would show that if you buy the Hilux, have money set aside for trans, injector, turbo and other engine repairs within the first few years.
Also note that they both use the same transmission but the L200 has additional cooling from the factory, leading to a better overall experience.
Features, well the L200 has more features, including the Super Select transfer case, than the Hilux. However, Diamond does not bring in the fully fully loaded model, and I believe it's the same problem at TTTL. Your best bet to get all the features are with the RORO dealers and in that case, the L200 out-features the Hilux.
Foreign tests have ranked the L200 higher in key aspects of performance such as acceleration, braking, comfort etc.
However, a major point to note is the aftermarket. If your goal is to modify into a mean offroader, then the aftermarket for the Hilux definitely wins over the L200. In fact I believe the L200 has the least options for aftermarket parts in the class.
I hope this helps.