Diesel is the way forward..
Ive got a 99 XEDi (L series) and its fab.. Plenty of torque for towing, and im getting 39MPG average out of it.. TD4 is also a great engine... They are two very different engines, but to the average joe bloggs theres no difference, both sound like a diesel (ie clattery) and both go like a diesel (ie slow!)
Got to be honest, aside from different dash clocks, i really cant tell the difference between mine and my mates 02 Td4!!
If 1 had a budget of yours and i had to choose between a 2000 (v or w reg) L series with 90k on the clock, or a 2000 onwards Td4 with 160 on the clock, id go for the L series.
Whatever you choose, try and make it a L series of Td4 diesel - both are fab engines and ecenomical too...
Petrols are usually prone to failiure, but as mantamad says, if you can find one at a good price that suits your budget.. then consider it.. But you WILL have to do the head gasket at some point, so budget for that too..
Good luck