Wilton's is short, I've heard, and I've used Earlene's but she doesn't have as many size options (looking for 3 tier square for 125 people).
Any other reputable cake serving chart out there??
Squares are fairly easy, using a 1"x2" 4inch high as a serving.
The accuracy of the cutting chart also depends on the skill of the server.
I usually go with a number between Wilton and Earlene.