In almost all cases of someone running a single pipe that I notice, it involves someone moving from a stock exhaust, or a fairly unmatched pipe for the persons motor, over to the single pipe. This passes straight over the pipes developed for the persons desired riding style. Example: Average Joe member comes in and says I just switched from FMF Fattys over to the single pipe on my stock bike with a pod for trail riding and it has tons more bottom end. One of the correct first pipe choices in my eyes is the FMF Gnarley for a low-mid pipe. The Fatty is meant as a midrange-top end pipe in the FMF line up, of course it is not suited as a low-mid pipe. However, the FMF Gnarley was developed for this exact instance (low and midrange power emphasis).
I do not tell someone to build as exactly I did. I suggest what I would do based on my opinion and hours upon hours of testing and tuning with the components DEVELOPED for the particular power range they are trying to achieve the most emphasis in. I run pro circuits, but you will find me suggesting pt mids, fmf gnarleys, and pro circuits as a low-mid range pipe to try. I run Mikuni TM 28mm carbs, but you will find me suggesting 28-30mm pwk's, lectrons, and TM's for a low-mid range carburetor.
Shearer makes a true drag pipe, but the cpi setup is meant as a mid-top range pipe from the testing I have seen and from the info I have acquired on them. So it does not suprise me that you are happier with shearer pipes as a drag racing pipe. I would suggest a cpi in a mid-top pipe choice. I would suggest a Shearer over that pipe for someone looking to drag race.
If you have a lot of specific information on something that is backed by lots of testing, tuning, and has been cross analyzed with different setups, on different motors, then yes you should tell people they are wasting their time and money in the direction they are going.
Another thing with single pipes on sleds is this. Snowmobiles typically operate in one rpm range and use clutching from the cvt to obtain the desired power delivery, acceleration, and engine braking. A banshee uses an entire rpm range and requires direct clutch lever application, and gearing choice to obtain desired power delivery. That is another reasone (besides fitting the pipe under the hood) that single exhaust choice on a snowmobile is not as critical as it is on a trail ridden banshee.
All too often someones opinion on here is based on using 1 or 2 singular products and basing a result off this. Not many people feel the need to test more than 2 options on something because of the obvious time and money requirements to do so. When average Joe member comes in and says " Hey my 2 into 1 pipe works awesome" it is based off of the limited testing they have done. All to often you hear, well my bike hauls ass, or rips, or runs great. Im sure it does based off of the parts those individuals have picked. Had they optimized their choices correctly for what they are doing, they more than likely would have seen even bigger and better results from their setup. I.E. picking a set of low tensions carbon fiber reeds for a trail motor over a set of vforce reeds which are meant for max intake airflow and not max intake velocity (desired for faster acceleration with less peak rpm).