In general, higher wattage means more heat - though of course, the size of the oven, the temperature of the element, and the insulation will all play a role. On a pizza making forum, a member did a survey and according to the responses, the average oven had 6,000 watts when you add the top and bottom elements. Again, I think it is tough to just compare wattage across brands, or even oven models, since size of the oven can be a major factor. Those of us with combi steams have very small cavities, most under 2 cubic feet, but they heat up extremely quick . So if you are looking at two ovens from the same manufacturer that are the same size, in general the one with higher wattage should heat up quicker, and recover quicker.

"Is this a correct assumption?"

No, this does not translate into faster heatup times on ovens.

I think you are obsessing over something trivial. If ten - fifteen xtra minutes of preheat time on an oven are going to cramp your lifestyle , then you really need to be cooking with a microwave or a TurboChef oven.

Best to focus on build quality, strength of the company providing support after the sale, the user interface, i.e. knobs, buttons, dials, display, computer or lack of, ect...and styling.

An oven is not an instant gratification tool, unless Apple rolled out an iOven this week while I was on vacation.

Xedos, thank you for the response. I like to have an oven that returns its heat quickly when opened a few times. Baking is what I do all the time. It is interesting indeed that many oven makers do not exactly flag their oven wattage around, including Thermador, I had to call for their wattage info and it is low! In fact, Jennair is higher. However, what I like to know if it makes a lot of difference.