Hi,
Just thought I'd jump in here because we're just past the point where you seen to find yourselves. At the two year point, we were pretty well convinced that a diesel pusher was the way to go. We currently have a smaller gas rig and we are looking to travel to Alaska in a year or two.
We're currently traveling in the western part of the country (Rockies) and its demonstrated that the gas/diesel issue is not primarily one of power. At just under 20,000 lb. and having a Ford V10, we're getting around just fine. We pass some trucks and others pass us, but the time you spend on the hills is a tiny part of the RV experience.
In the other times, we enjoy the RV we bought and, having gotten my ego under control, the diesel urge has pretty well gone away. Today, I spend more time thinking about improvements; inverter, full body paint, upgrade computer stations, etc. I'd urge you to decide based on what you want (floor plan sound familiar) or need (washer/dryer?) rather than DP or gas. I'd also go slow, its taken us over two years of essentially full time travel (35,000 plus miles) to figure out what we want/need, and I'm not totally confident we're there yet.
Either way, enjoy! Life is short!
Ernie
PS Its not a cost issue for us; just a decision on trade offs - size (smaller is better for us) vs. benefits.