I have owned both. My first motorhome was a Rexall 32 footer with the Ford V-10 and the current motorhome is a Tropical 35 footer with a Cat 330 HP diesel. If I were to race those two motorhomes side by side in the quarter mile the V-10 would win the race hands down. It had plenty of power for a 32 footer and the acceleration with the gas engine was much quicker than the diesel. What I got with the diesel is a much smoother ride and much more capacity for both carrying and towing.
Both motorhomes had 100 gallon water tanks. With the gas motorhome I could tell how much water I had in the thank based on performance. I could really tell when that tank was full. With the diesel engine I can't tell any difference between an empty water tank and a full water tank. The same was true of having the toad along. I towed a Jeep wrangler when I had the gas motorhome and it towed it just fine, but I could tell when it was back there versus when I drove the motorhome without it. With the diesel motorhome I couldn't tell the different in power with the Wrangler or without it. I now have a much heavier toad, a Dodge Dakota 4x4, and I can tell when it's back there, but the DP pulls it just fine.
So to answer your question it's all about what you want. If you're going to be spending a lot of time in the RV and traveling all over, you'll probably like a DP better than a gas rig.