Friends have used the Whisperlite, though I have not. I've had a Dragonfly for fifteen-plus years now, and have used it in Canada, the US, and southern Africa, from sea level to 15,000 ft, with all manner of fuels. It's been faultless.
I no longer use the Dragonfly for cycling or hiking, because I've found a lighter & more compact alternative, the Trangia alcohol stove.
I still use the Dragonfly for paddling, where its extra bulk and weight (by comparison with the Trangia) are less of an issue. The Trangia's one negative by comparison is its fussiness/inadequacy for simmering: it does, after a fashion, but the Dragonfly is streets ahead.
Other options? I have used the MSR remote canister stove, and its pretty good if/if you can get the replacement canisters, and then recycle them. The setup is light, convenient, quick, and simmers very well.
Hope that's helpful.