I believe that the OP is correct, although I have never been told why. I noticed this when I saw the Kenmore induction slide-in right next to the free-standing at The Great Indoors. It was very obvious, but the salesman didn't know why. I think it's because the controls are on the front of a slide-in, so all the electronics (and whatever else) that are on the back of a free-standing are on the top of the slide-in, resulting in a lower ceiling in the oven. For the Kenmore induction ranges (according to the website), the slide-in is 4.2 cu ft and the free-standing is 5.8 cu ft - that is a big difference!

I'm planning on the GE Cafe gas range that cluelessincolorado has for my upcoming remodel. In our former home, we had a Maytag Gemini electric range w/ the double ovens and I really enjoyed having that smaller oven, also. Unfortunately, sounds like the GE Cafe's smaller oven does not heat up quickly, unlike the Gemini, due to the former using only a 110 volt circuit. It's one of those tradeoffs that I have decided is worthwhile for this time around, though. Among other things, the Gemini burner configuration squishes all the burners to one side and puts the controls on top, just to the rt of the burners. I am also trying to avoid having the raised back panel, plus I want the 5-burner configuration this time. Other than that, though, I enjoyed my smoothtop electric Gemini.

Most slide in ranges come with a stainless filler piece for the space between the range and the wall so you wouldn't need to purchase a piece of counter for that area.

Your decision of slide-in vs free-standing will impact the counter installation. Counter material will not impact selection of range style. I switched from a free-standing to a slide-in range a few years ago and the range came with a little strip to fill in the gap behind the range. If I'd installed new counters, I would have had the counter fill in that space instead. The way that my slide-in installs, it may also have been beneficial (though not required) to notch the counters slightly in order to snug the range closer to the back wall. So when you've selected your range, make certain you have all installation instructions available prior to installation of the counters. A 30" range should be just that: 30" wide. You can usually check out installation instructions and specifications online to make certain, but as long as you currently have a 30" range in the space, the wide should be perfect for any other 30" range. Personally, I like the look of no built in backsplash on the range. That was my primary reason to switching to a slide-in. However, I've since found several ranges that are free-standing and have no built in backsplash. So, make certain you look at all of your range options before you make your decision on slide-in vs free-standing.