I think the A9L computer has better stock settings, but the TwEECer will let you adjust fuel, spark, etc to optimize performance to equal that of the A9L. Two big benefits of the TwEECER are:
1) Data logging (you need the RT model for this)
2) You can update your tune as you add mods to your car
I got one for my mildly modified 95 and it's helped improve performance and gas mileage.
There is a pretty tall learning curve and you will need to spend some time figuring out what to tune. If you like to spend time researching, experimenting and analyzing data and like computers then you might like the TwEECer. The user forums are pretty good and there is a lot of information posted and people that will help you out. Good luck.