A robotic cleaner is usually the best, but also the most expensive, and this is independent of the type of pump.
In general, the pressure-side cleaners are better than the suction side ones, but most pressure-side cleaners require relatively high pressure and flow to operate and typically use a separate booster pump that provides up to 50 PSI at a low flow rate (< 25 GPM). At it's maximum RPM of 3450, the Intelliflo, at 20 GPM it produces 94 feet of head, or 41 PSI, and this would be on a dedicated line. Because of this (and to reduce electricity costs by getting rid of the booster pump), I purchased
The Pool Cleaner (4 wheel pressure pool cleaner) that I can run on a switched dedicated line at the lowest Intelliflow flow rate of 15 GPM which results in 11 PSI with the cleaner attached and 4 PSI unattached so the cleaner has a pressure resistance of around 7 PSI at this flow rate (their recommended wheel RPM rate is 11-14 and the 15 GPM flow provides just over 14 wheel RPM which seems to work fine). I first tried to run the Intelliflow with some flow to the regular returns and some to the cleaner, but this didn't work out very well. Though some people just attach The Pool Cleaner to one of the return lines and let it run whenever the pump is running, I didn't want it interfering and it seems this wouldn't work very well if one has more than 2 return lines anyway (I have 3) as too much flow gets diverted to the "open" returns instead of going to the cleaner.
Suction flow cleaners are like The Pool Cleaner in that they do not require high flow rates nor pressures, but attaching one to a skimmer does reduce skimming action. There are a lot of people who love their Kreepy Krauly, however. My guess is that it won't be as good as a pressure-side cleaner with a dedicated booster pump nor as good as a robotic cleaner.
I've been happy with The Pool Cleaner, but I also have an automatic electric safety cover that covers the pool when not in use so it doesn't get a lot of junk in it. So I can't say how it will work in an environment with more junk to clear.
Richard