I've seen prices of later Td5's now overtaking TDCI Defenders as longs as they are clean, I buy Defenders on condition rather than a specific year.
I find the Puma interior even more cramped, looks better though. The 6 speed ZF gear box, whilst being nicer to use than a R380, it's becoming apparent that they are not as strong as the R380 box and it seems that they are not worth rebuilding.
As for being investments, I'm not sure, I bought mine last year for £15,000, and am now into it for £31,000, my choice, there was nothing wrong with it, just its primary job is to go to Morocco and back without falling to pieces.