Having had both a electric and gas roaster I can say from personal experiences they do roast a little different. There is a understand on this and to why they roast differently also. Don't quote me but a gas roasters going to have a solid drum so conductive heat is going to play much more of a part in the roasting process. Where as a perforated drum is on a lot of electric roasters. You are still going to get conductive heat however a lot of the heat transfer to the bean if going to be convective heat.
Conduction and Convection, in my opinion two important components in roasting along with many many other aspects.
It may be a personal opinion ans as i said having had two types of roasters one being gas and electric i found to have more control over the gas roaster for one. Flavors after roasting on the electric where a little more muted than those on a gas roaster. The repeat ability on the gas roaster i owned however was a lot easier to achieve mainly because the roaster had two set and forget temps for start and stop. Where is a gas roaster you will have the ability to adjust gas and on some 2kg roasters air flow. Once again coming back to conduction and convection.
So i guess i ask when you say quality, both can produce great coffee, everything i have said above is knocked out by the person who is roasting ans the knowledge they have. Thats whats going to produce the quality.
Just my two bob.