Tom,
I'm on my third M3 exhaust and hope to save you some pain. I'm not an expert and most of my info is hearsay as you have already experienced. It's a very tough decision, but we also all have very different budgets. I knew of only two choices when I first began looking. I knew that the Borla was well made, stainless, and reputable. Whether you like the tips is personal preference. Also saw the Tri-flow ad in Roundel. It costed $700 at the time. Makers of tri-flow stated that the Borla only increased HP by about 5hp. That , of course was a biased opinion. But, being alone and new to the BMW world, I was suckered into purchasing their exhaust with a claim of 19 added HP. This however, was with the Autothority chip for which I ended up with the Dinan chip. Nevertheless, construction was fairly good , made of stainless steel, and bolted on with no modifications. However, being a perfectionist, I was disappointed that one tip was a mere 1/4 inch lower than the other. The exhaust was wonderfully super loud,deep, aggressive and burblely. Soon, the Supersprint became popular, but the price went up $600 to $900 making the TriFlow a better bargain. Due to budget constraints, this made the decision for a few people on the digest to buy the TriFlow. Overall ,people really liked it, The sound and subjective power increase. Then I began hearing about chip developement based on the Supersprint products and decided to change at a big loss. Yes, I spent another $900. Ouch! I was unhappy with the different level of the tips , plus I like the upswept DTM style tips of the Supersprint. I also heard about some guys that flow tested a bunch of mufflers for the M3 and found the Supersprint to be the best flowing. The stock muffler was also found to be excellant and better than some upgrades. I don't think Borla ranked very high. The Supersprint was very well made and also had attachments for the stock heat shield. The catch is that the pipe ends required modification (cutting and welding) to fit, thus increasing cost even further. Overall, I love the fit, looks, construction , and sound. In fact, I find it just as quiet as stock, plus it is very smooth. No sputtering and rhythm undulations as with the TriFlow. I miss the loudness, but the radio sounds better now. With the direction I'm heading, this quietness won't last too long.(another story).

Bottom line, the best is what you can afford, but the Supersprint would be the best choice if cost no object. Just make sure you skip the step up cost which I had to take a loss. If the Borla costed say $300, hey go for it. That's $600 less plus modification/installation costs. We all have different objectives, and mine was to match as closely as possible the setup for which JimC. as tuned the ultimate chip for the M3 with regards to just bolt-ons and normal aspiration which he has already reported on the digest.

Scott H.