"Ignition & Growth" (I&G) and JWL++ models are compared for a variety of problems. The detonation velocity becomes nearly constant with zoning at the edge of convergence, which for TATB, is 8 zones/mm for I&G and 4 for JWL++. The use of pressure in the rate for I&G makes the detonation velocity rapidly decrease as the zones are coarsened. Using pressure plus artificial viscosity to some power in the rate for JWL++ allows the correction for coarsening zones. In coarse zones, the pressure and the burn fraction turn on independently and this feature dominates model behavior. If pressure lags burn fraction, then the maximum pressure will be lower than expected. An unexpected phenomenon is saturation, i.e. the slowing down of the detonation velocity as a function of the fast rate constant. This slowing can be weak and produce a plateau. or it can be strong and cause the detonation velocity to approach an asymptote. The saturation effect comes from a combination of the 1 - F term and declining pressures. Failure (critical diameter effect) occurs in reactive flow but optimizing for this undoes the settings for other results. In JWL++, the fast reaction pressure exponent is near -1 for the best fit for the size (diameter) effect, 2 for the Pop plot and near -3 to fit failure. The Pop plot deflagration rate is derived, although it needs not to be the same as the detonation rate. The use of additive pressures is compared with the pressure equilibrator and no difference is found. Increased zoning by a factor of 5 and improved code structure will be needed for future improvement.