There are pluses and minuses to both options.
Lasers work such that if the correct distance is observed, they avoid overheating the tissues. In the mouth, though, it becomes very difficult to completely control the angle of the laser and where it heats tissues. If mistakes are made (and they are easy to make) damage that is irreversible can be done.
On the other hand, using a scalpel blade and removing the tissue leads to significant bleeding. This bleeding stops, but dogs tend to be sore for a couple of days. INfection is also a concern if the mouth is not kept clean.
You will hear both of these arguments, depending on who you ask.
Personally, I prefer to use a scalpel blade and avoid the laser in this situation. I treat my patients aggressively with pain medications and control infection with clean procedures and antibiotic coverage.
I hope this helps!
As always, if you have further questions or concerns, please don't hesitate to ask them using the "reply" function.