Using my great (ahem) knowledge of stoves, I'd like to give you a definite: it depends.

I own both stoves. My clear preference is for the Omnifuel. It's build quality is far superior. Among other advantages, the the Omnifuel's ability to run on canister gas is plus for inclement weather where one wants to cook inside a tent or shelter. Priming inside a tent carries a not insignificant risk. There's no priming with gas.

Gas for younger folks is in my opinion safer since there is, again, no priming. If your son is about to turn 18, that may not be an issue, but if he's 9, then that's a consideration. An Omnifuel can grow with you, so to speak. Canister gas for when you're young, and then "advanced" fuels when you're more mature.

Now, having said that, neither stove is inexpensive, so I imagine cost will be a factor in your decision. The Primus Omnifuel retails for about $160, the DF for for $130. There are a lot more DF's sold than Omnifuels. You probably could pick up a used DF for quite a bit less than an Omnifuel. The Dragonfly wins hands down on cost.

The silent caps for each stove are yet another expense. I've seen them go on eBay for more than the price of the stove. Serious sticker shock. The Omnifuel, if one were not going to get a silent cap, is the quieter of the two. As for the caps themselves, they have my whole hearted, unequivocal endorsement, an endorsement shared by many fellow stovies and a friend of mine who is not only a long time stovie but also a machinist. Quality stuff. If hugecanine has offered to make you a custom cap, I'd say go for it. I've purchased multiple items from him, and I sent a stove to him for repairs beyond my capability. He does good work. HOWEVER, having said that, he does make something called a midi-cap which is a more generic cap. The midi-cap can be used for sure on a Dragonfly and I believe also an XGK and an Omnifuel. It doesn't have the legs to hold it in place that a custom cap would, but you could use it on a wide variety of stoves if they have similarly sized burners. Consult the maker re what stoves it will fit. If you can afford the cost, the custom caps are the better way to go; if not, the versatile midi cap is a good choice.

So, there you have it, my definite "it depends."

Hopefully knowing some of the tradeoffs and considerations is helpful.

HJ