I went from a T6 -> Aspx -> Python.
The money gap between the T6 and Python is huge - so set your expectations for a longish haul.
The T6 is amazing value for money, relatively cheap to buy/upgrade/repair and, excepting combat, good at everything I tried it for. It has great speed, superb jump range, and plenty of internal slots. I'd rate this as one of the best vaule for money ships in the game.
The Asp I found was a huge and expensive disappointment by comparison, and imho overrated. The T6 does nearly as good a job in many regards, for way less money.
The Python is now my main ship (...at least until storage...) and is proving an amazing all-rounder, even if it is a bit on the slow side and unjumpy. However I can see no reason to go back to the T6 unless maybe I wanted to go exploring.
Bottom line, the T6 and Python aren't really comparable, not at the price difference.