a thick atmosphere that will protect against radiation (the extra distance from the Sun also helps)
Lower gravity (and atmosphere) makes access to and from nearby space easier
Thicker atmosphere and lower gravity makes aircraft and helicopters an easy and effective way to move people and cargo around Titan
More things in relatively nearby space to explore/mine
Easy to cool machinery etc to the atmosphere
Possible subsurface ocean -- not quite sure what this is good for, but its interesting
Some advantages of Mars are:
Abundant iron and other heavy elements
Usable solar power
Gravity closer to Earth's (may be relevant for health, we don't know yet)
Much warmer -- and less heat loss to the thinner atmosphere
Three to six months from Earth using about 4-5 km/s of delta-V (from LEO) versus 3-5 years to Saturn system and about twice the delta-V
Radio takes a few minutes instead of an hour or so.
Both have abundant water ice it seems, and carbon (CO2 on Mars, methane on Titan). Mars seems like a more plausible short-term prospect due mainly to its nearness, but Titan may ultimately be the more valuable long-term option due to its nitrogen and its radiation protection.
The biggest obstacle of living on Titan is bound to be it's insane cold. People say space is cold, but space is a vacuum. A thermos bottle uses a vacuum as insulation. So wearing a space suit in a vacuum, in the shadows, it's not that hard to retain heat. There is no convection and conduction only happens on contact. However in an atmosphere that is only about 100 degrees above absolute zero you would have constant conduction and convection sucking away heat. -290F or -179C are really cryogenic temperature. I wonder if any fabric or rubber could be flexible at that temperature to even make a suit out of.
If we ever wanted to make very durable spaceships to go out among the stars somehow then Titan would seem to be a better place to set up shop for it, and you can tell, since, for one thing, we could mothball our expensive constructions better if we put them under the protection of a thick atmosphere, for example, and, for another, Titan is the place that would accommodate the bigger payloads.
Some rough calculations would lead you to think that if maybe the interstellar travel would require such pressurized drums that they may as well have cattle and farms in them then simply getting them up would seem to become a tall order from as soon as you build them in any place that has much more gravity.
Unfortunately, Titan can't be colonized at all despite being the most Earth-like body (other than the Earth itself) in our system. Quite everything on Titan is Earth-like except one factor: gravity. Titan's surface gravity is less than 1/7 that of the Earth so the body of a colonist would radically change and effects on you would probably be similar to these of microgravity. Other Saturnian moons have even much lower gravity. So the only ways to colonize the Saturnian system would either be a rotating spacecraft creating Earth-like gravity in orbit around Saturn or one of its moons (from which one could visit Titan and other moons) or a floating airship on the equator of Saturn where the gravity is 0.93 g (from which one could also visit Saturn's moons if you manage to go around the rings as most of the moons orbit above the equator). If Titan had the same density as the Earth, Titan's surface gravity would be around 0.405 g which would be more than that of Mars but since Titan consists of a subsurface water ocean and ices, it has a low density. Therefore (and because of the distances of course) it is so much easier to colonize Mars having 0.38 g.