IMO the TD5 has more torque than the tdci if you get it remapped and sounds better. I do prefer the six speed box in the tdci as it feels a nicer box and it cruises better on motorways.
I don't think either engine is more reliable than the other, apart from the tdci being newer, so getting one that has not done much work would be easier.
Seems to be quite an overlap on prices between Td5 and tdci, so I would assume that overall the market likes the Td5.
I haven't had any hassle with my Td5, but I am not enjoying the R380 box after driving a tdci with a Getrag 6 box which was much nicer.