There are many different kinds of pool cleaners, each with advantages and disadvantages. For some background on the range of choices available, take a look at Automatic Pool Cleaners over at Pool School.
I have a suction side cleaner (Pentair KreepyKrawly SandShark). I also have dedicated suction port separate from my skimmer basket.
If I only had my skimmer port to work with, I'd probably get annoyed with having to play with a suction splitter and regulator to get the KK to work with skimmer. I'd likely go with a robot.
It's also important to note that a suction cleaner should also have an inline leaf bag canister to catch debris so it doesn't get into your suction line. I got a really bad clog in my suction line (**** mesquite trees!!) because I did not have an inline leaf canister. They will slow a KK down a little but it's well worth the $50 to not have to deal with a clogged line.