Im not quite sure what you're asking. There is a world of difference between a gas and electric grill. Either can come with an electric rotisserie attachment. The presence or absence of the electric rotisserie really has no bearing on the grill's performance.
However, if you're asking if an electric rotisserie works better over gas or charcoal grill, that's a different matter. Gas grills are constant and require little attention once lit. This makes them simple and easy heat sources for a rotisserie. Charcoal grills, on the other hand, require attention in order to maintain consistent heat output. The advantage, however, is that meat roasted over a charcoal or wood flame tends to have better flavor, IMO. So, I tend to favor charcoal grills over gas with or without rotisserie attachments.
If you're looking for something to use occasionally or on the weekends, and have no interest in smoking meats or using alternate fuel sources such as wood/charcoal etc, a gas grill with an electric rotisserie will work just fine. However, they tend to be a bit more pricey.
The stand alone electric rotisserie ovens are notoriously difficult to clean. There is a recent wind up system on one of the fund-me sites that would work in a regular oven, on a grill or most anywhere. It breaks down for comparatively easy cleaning, I think even dishwasher safe?
Ok, so the Kickstarter was last year, it's now commercially available on Amazon.