Ibby!...Montreal?...WTF?...
OK, back on topic...I have both a tracer unit and a couple illuminated mags. I prefer the Unit to the Mags mainly because the with the mags the LED charges the bb's before they enter the hop-up whereas the unit does so after they've left it. This means that any bb's in the hop-up chamber ,waiting to be fired, will likely have gone dark by the time you fire them. Perhaps I'm nit picking but I want that first burst to glow damnit.
I'm not bothered by the muzzle flash as , was mentioned ealier, tracers work both ways. I would add that if you can see the flash from a tracer unit you are looking right down the barrel and a bb is already on the way, heh.
IMO what is more important than what you use to make your bb's glow, is your method of employment. For instance, if you are the only guy on the field to have one then you can expect every enemy who can see it to send a few your way. But if on the other hand your whole squad has them and you bump into the enemy, it will be a completely different story. You will be able to quickly concentrate your fires without the generaly associated CCC issues. You also would gain similar psychological benefits to yelling/communicating loudly and making it clear to your enemy that you are comming to f%#k him up. Basically Shock value.
Used wisely they can be alot of fun just try to avoid being the only one on the field.
J