Strange as this may sound, for regular servicing, the V6 is probably the better bet.
This is because every three years for the 2.0 TS/JTS, you need to replace the timing belt, timing belt tensioner, timing belt idle bearing, balance belt, and balance belt tensioner. Every second belt change it is also recommended to replace the waterpump, and also possibly the variator (particularly if the variator becomes noisy).
On the V6 you don't have a balance belt and tensioner, and you don't have a variator to worry about. Also, the 916 V6 should have the metal impellar waterpump, which is nigh on bullet proof.
Obviously both engines demand regular and meticulous maintenance, with 6,000 miles oil/filter changes a good idea (Alfa engines like clean oil), but the TS engine in particular does have a propensity to use oil, sometimes to the point where you need to check the oil level every week if doing high mileage.
In summary, both engines are good, but the V6 in essence is a much more reliable and robust engine than the TS. The V6 is also much more fun, sounds much more fun, and with the top down, is extremely good fun. It is the last of the real Alfa Romeo engines, and it is quite possibly the greatest V6 engine ever made in the history of automotive engineering.
If that doesn't persuade you toward the V6, nothing will.
I think you have just about persuaded me to get a V6