I learnt on a tri and am now doing tail wheel training on a Super Decathlon. I love it, and went solo for the first time last week. I can only speak for this aircraft, but it is certainly harder to control (or should I say takes more care and pre-empting and preventing what is about to happen next) on the ground. Take offs require more directional control and landings are less forgiving and speeds are more critical (particularly in the Decathlon with no flaps).
I know it is improving my flying skills no end, and I am sure it will get rid of some bad tri habits of landing a little too flat.
As the other chaps have said, it really comes down to what is available to you, how much you have to spend (I guess taily's a generally a little more expensive as less common these days), and most of all on the instructor. If you are taught well in a tri, changing over to a taily should not be an issue. I went solo after 2 circuit sessions.
I have also found doing this after has brought more excitment into flying. I cant imagine it the other way round, ie converting onto a tri after learning on a taily (IMHO).
either way, enjoy.
JB