I would go for the ability to keep improving the car, you get used to the extra performance and it's nice to be able to do a number of upgrades. My car came with a revo map, I then did some hardware changes over time and finally got the custom remap. Each time the car improved and I enjoyed it for a while before making further enhancements. I was pleasantly surprised by the difference the full Milltek alone made. The air intake seemed to make no difference. Not sure how this translates from a TDI to an S3.
Love the car, even though I've bought another car, I just couldn't sell the A3.
What's your priority? Maximum enhancement now, or getting gradual enhancement over time.