I dont have a business yet but lurk here quite a bit. If you want opinions here ya go with my 2 cents:
FEC100 - NSF approved, pellet driven smoker that can reach high temps which can be used for chicken. You want to get to at least 325 F to get a nice crispy skin on bbq chicken. Electric so you will need a generator or power source but it only draws 300 watts. Rack size is 23"x17" so a rack of ribs fits well. Nice electronics that can reach a temp and then go to holding temp. Can be used for cooking and holding dishes but will have smoke flavor as heat is from burning pellets.
SM150 - NSF approved, Cookshack runs on wood chunks, electric so you will need a generator or power source. Gets to 300 F, possibly high enough for crispy chicken but fairly good if not. Also has nice electronics that can reach temp and go to a holding temp. Has 1500 watt element so that will take a bit of power. Has 18"x18" racks, so you might have problem with a full rack of ribs fitting. Can be used for holding food and cooking of side dishes.
There is quite a price differential between the 2 units ($2900 versus $3300) with different capabilities afforded by both. Personally for mobile vending operation I would go with the Fec100 - small footprint, low power reqts, high temps when needed. For restaurant, I would go with the SM models.
One other thing, I would recommend skip making your own sauces until you get well established, buy Cattlemans at Sam's or Costco and doctor it up.