Im not sure if i agree with you on that one. Certainly when a glow and a diesel are spinning the same prop on the same displacement the sound will be comprable but the glow will have a slightly higher pitch which seems louder to me. However, one of the main benifits of a diesel is its ability to swing larger props, thus lowering the rpm and dBs (props are a lot of the noise). This lower rpm and added thrust from the prop also provide for the added fuel efficency of the diesel (I like mine @ ~7000-8000 max rpm). Another benifit is the ability to run an exhaust extension (longer than a yard if you desire) on a diesel because of the tolerance to backpressure, somthing its glow counterpart would be severly hampered by.

That being said, I have found that diesels are definately more complicated and take some time to getting used to the costs are close to glow with the inital engine cost being more for the diesel. I echo LouW; in that if you want less fuss, go with the glow, but if you want to try something different diesels may be for you.