I would HIGHLY recommend buying the T6 with the 3.0L inline-six (not the new 4-cyl). These T6 engines are said to be underrated from the factory in the torque department, and if you need any more power, you can get it with the P* tune from Volvo. Most importantly, the T6 is easily the most reliable engine out of your choices. The T6 is not a T5 with an added cylinder on the end; they are entirely different engines. Without getting into too much technical stuff, the T5 has a timing belt which requires maintenance and could cause your engine to skip timing (which would instantly destroy it). I have heard of countless catastrophic failures on low mileage T5s, but never on a T6. The T6 has no such issues, and are known to last for lots of miles. The only downside is fuel economy with the T6, which is not great.