I had an opportunity to compare the JDS Accu-Miter, Incra
Miter Gauge, and Mark
Duginske's FastTrak Deluxe Precision Miter Guide and offer these observations.
The Incra has the greatest granularity, normally locking in a CNC Laser-cut V-notch at any angle from -5 to + 95° (best feature). You can shift to +/- 1/2º increments by repositioning the screw-on handle, though it is risky because you can easily forget that you have shifted the scale. The FastTrak locks by repositioning a shoulder bolt and can be set at 0º, 10º, 15º, 22-1/2º, 30º, 45º, 60º, and 90º (least convenient). Most holes have a brass bushing. The JDS locks with a shot-pin (captive spring-loaded pointed pin) and locking screw at 90º, 45º, 30º, 22-1/2º, and 15º. Because they are all CNC machined and from various forum responses, I assume they are equally accurate once properly adjusted.
The JDS must be ordered for the saw for the miter bar to fit properly (longest lasting but biggest pain to get right). The FastTrak and Incra have adjustments to force the bar to one side of the slot (easiest but wears faster).
FastTrak has the greatest range at 180º (+/- 90º). The Incra's range is 55º, but can be reconfigured to the opposite side -- a process that requires tools and a lot of fussing. The JDS adjusts 90º (+/- 45º). Incra's approach allows it to have the largest scale (good) but cannot be moved to the opposite side of the blade on most saws without significant reconfiguring (bad).
Fences adjust horizontally along the gauge and are bolted into position. All have extruded Aluminum Anodized fences. The JDS' is heaviest and has the most T-bolt tracks. It uses two lever head bolts that can be very tight, but will not rotate 360º without an inconvenient ratchet action. The FastTrak uses Brass thumb screws and the Incra requires an Alan wrench (dumb but fixable). I find the fence must be adjusted whenever the angle is changed so it should be convenient but secure. The Incra's fence is the shortest and lightest.
The JDS and FastTrak have very convenient flip-stops to set the length of cut. The Incra's much flimsier, do not flip, and more difficult to adjust. However it has a toothed 1/32" rack like their router fences and a sliding scale. The JDS' fixed scale is useless because the distance changes with each angle (duh).
The FastTrak is the lightest, then the Incra, and the JDS is heaviest. I don't mind the weight but many people do. All are larger and heavier than the junk gauge that comes with tablesaws.
Alas, the perfect miter gauge still eludes (IMO). I have had a JDS for several years but turn to shop-made sleds for most tablesaw cross-cuts. I cut most angles with an AngleWright protractor between the sled's fence and work.
Shop Notes Magazine has a Miter Gauge Review on their site that is worth reading, but does not cover the FastTrak or Incra, but includes the Osborne Miter Gauge. I do not find the Osborne's method for setting angles as precise as the others, though I am sure others may disagree.