I had a lot of conversations with other diesel owners at BusFusion including TD vs TDI. To sum it up:

If you want great power and speed you go TDI. And accept the added complexity that comes with it. 
If you want simple and reliable the you have AAZ written all over you. Simpler conversion, simpler to keep on the road. less power, not as fuel efficient. 

Neither is cheap, and while YMMV you'll still like that improvement. 

Regards, Peter Kraiker 
http://studiofstop.com

On 2011-06-17, at 16:25, Mike Miller <mwmiller6@ATT.NET> wrote:

> Van-illas,
> 
> Please lend a hand if you have an informed [or uninformed but amusing]
> opinion about the relative merits of TDIs vs AAZ diesels.
> 
> Thanks,
> 
> Mike