I suppose it would depend on what your build type is, what liquid you vape, and what per you vape it on but FWIW here's my thoughts.
I prefer to use round wire builds for the simplicity. I'm currently using a 26ga, 6-wrap, 3mm Kanthal coil at .85ohm on an unregulated squonk mod. I wanted a single coil rda primarily for its efficiency and ease of use for travel purposes. Flavor is the most important but I like to have a moderate amount of vapour production.
Between the Hadaly and the Entheon I get similar flavors. The Hadaly allows for a larger build but since I use simple coils, the Entheon works better for me since it's a bit smaller in chamber size. The Entheon leaks/over-squonks less and therefore gets my vote for similar flavors.
If you already love your Hadaly I see no really good reason for you to make the switch. If you don't currently own a Hadaly I'd go for the Entheon because they are much easier to find (authentic ones are, anyway).
I have loaned out my Hadaly since the Entheon has become my favorite. It prefer it to the Wasp Nano, the Armor v1.0 clone, and the Pulse 22. I also have a Narca clone and basic rda clone on the way to try out.
I have an authentic Entheon as well as a YFTK clone. It is VERY difficult to tell them apart even while vaping (since I have identical builds running on identical mods).
I also have Hadeon caps for both (in both SS and clear). They still perform well but I prefer the original Entheon caps.
Hope that helps someone.