Vios has VVT-i but Sentra has VTC, so not much different. Sentra 10 years old technology equal to Vios current technology.

My previous Sentra 1.6SG MT, for highway drive I can get around 17-18km/L with 90-110km/h of speed. For city drive, I can get around 11-12.5km/l, if really want to compare with Vios, I think Sentra will has slightly higher FC due to heavier body and bigger displacement engine. But if you really want to compare with current technology, then I think take Sylphy/Altis as examples, I found these 2 models have good FC with heavier body and bigger displacement engine.

Vios also not bad if you mean for dity driving, as for the maintenance, I don't think it will be very high for Vios. I think you can make some survey about the maintenance cost, but do remember, send back to UMW for service will surely expensive than service outside, but within warranty period, you have no choice but send back to UMW. Do becareful about the current Toyota products, heard their quality isn't very good nowadays.

My previous Sentra, if I not mistaken, it ran around 380k without any problem, no single "makan minyak hitam" problem at all. But that was my company car, now sold already and my company already purchased new Altis in 08. I still miss the Sentra a lot because of much better "driving drama" if compare with current Altis. And Altis durability is still lag behind the Sentra, at least I have sent in UMW to fix the dashboard and rear suspension more than 5 times, and the problem will come back after a few weeks .