Hi! There is no difference in the burn rate between the top and rear vent models. The two options are for installation ease as you mentioned. Rear vent for fireplace installs and top vent for a "free standing" install. Though this of course depends on a variety of factors but as mentioned both stove perform the same and have the same specs. Please feel free to contact us at anytime with any questions. We are happy to help in any way we can.