I mainly use Smartlines after I had a few problems with Hunter controllers a few years back. They have stacks of great features such as the inbuilt diagnostics that you mentioned, also inbuilt locator, seasonal adjustment by month (I-core now do this), test cycle in 10 second increments, grow in feature which is a temporary program for new landscapes. Once the days you set it for are up it reverts to the normal program you want. Programming is very easy also. I have installed about 80 or so 1600 and had zero problems.
The only thing I don't like is the speaker terminal inputs for the wires. I would rather screws. It also gets a bit tight in the box when you have multiple cable strands, and just the one common terminal isn't enough for a controller that goes to 16 stations. The SL4800 has more room though. Looks the same as SL1600 on the outside just in a bigger cabinet.
The wireless weather station signal doesn't seem to be as strong as a Hunter rain sensor, as I had one job where I had to ditch it where it was in a concrete bunker thing around a pool pump, but the wireless Hunter rain sensor works fine in the same location.
I have installed Smartlink at 3 locations so far and the clients are very happy with it. I think it's awesome for the price compared to the other options. Just waiting on the flow sensor to become available.