Well, Chronos Clocks are the most heavy duty. However, they cost over $100 and my Chronos GX had to go back for repair. But the other Chronos Clocks seem to be working fine with all the other people I know who have them, and after that it's just a decision between the sensor ones or the push button Chronos.
Chronos GX are easier to set, but smaller. They also don't show tenths of seconds, like the longer Chronos' do. But I found the GX just fine (besides the problem with it malfunctioning), and simple to program.
I've never had a long Chronos clock, but several of my chess friends do, and they've all said that Chronos' are very durable. The longer Chronos are harder to set, so I've heard. The only other con about Chronos clocks are that they are hardly ever in stock, because the manufacturer nearly stopped making them. :(
The next clock would be a Saitek Competition Pro (which I currently have to hold me over until my Chronos clock comes back), which is silver and black, if colors mean anything. Also, they have push buttons and are pretty easy to set, once you get the hang of it.
Hope this helps! ;)
Which chess clocks do you recommend? I'm considering buying one soon and would value input.