I've had both, and prefer the Intermatic. I think it is a slightly higher quality unit, heavier and more solidly built. Also, the interace is more versatile in the intermatic. I like to see the water moving if I'm home so I like my pool running for a couple of hours in the a.m., and many hours in the afternoon. No problem for the intermatic; for the tighwatt, you can run two cycles per day, but both cycles have to be identical in length. I'm a tinkerer, and I prefer to frequently fine tune run times, and the intermatic allows me to do so more readily. The tightwatt is pretty much: set summer run time, set winter runtime, and the unit's algorithm does the rest. Some will prefer this "set and forget"; I pefer a little more control.
One can add a wireless remote for both. The tightwatt uses an x10 system, which gets so-so reviews but is pretty inexpensive. The intermatic utilizes it's i-wave system, which is more vesatile, allowing for control of a heater and valve actuators, but is more costly than the x10.