A diamond blade is manufactured in two processes. The first is the core design. This is when the steel is shaped and tuned so that the diamond blades being made from it are high quality and long lasting. The second is the welding of the segments onto the actual core of the diamond blade.
Laser welded diamond blades will tend to have a longer life and cut faster than sintered diamond blades. Sintered diamond blades have a much shorter life than laser welded and typically will not cut as efficiently.
The laser welding process with diamond blades fires the segments onto the core. This leaves the bond much stronger and produces a much better quality product. A good way to tell if a diamond blade is laser welded versus sintered is to look at where the segment meets the core. A laser welded blade has a much rougher looking edge than a sintered blade which is pressed on. See if you can tel which is which.
All in all, it is worth the extra few dollars you spend on the laser welded blades. Contractors get approximately 35% more life from a laser welded blade than a sintered diamond blade.