All about the nic for me.
Started out with flavored juices for a while. Ended up on unflavored, mostly because I never got a good flavor experience. Honestly couldn't taste them, even when I switched things up, changed flavors often, and the like. I have a very muted sense of smell though, and it carries into my sense of taste. I have the same issue with foods, end up eating spicy stuff for the most part so I can get more taste from it.
Anyways, after moving to unflavored and honestly not missing trying to get a good taste experience from vaping, I was sold on it. Primarily becuase my coils/builds/wicking lasted forever. Also figured no reason to be vaping flavorings meant for food use if I wasn't getting anything out of it. The wife actually complains if I switch back to something flavored now and she can't stand the smell of me vaping flavored e-liquids.
Anyways, LOVE unflavored juice. DIY is a sure bet for me and ridiculously inexpensive since I'm not even adding flavorings. Plus, I can change my nic levels at any time. Currently using 2.4 mg when I sub-ohm and 12mg when I toodle puff. I know I can find premixed unflavored for a around $35/gallon (3mg), but still prefer DIY so I can control the VG/PG ratio and nic levels and can mix it for much less than that.
Agree that dropping the nic completely will be a good way to know for sure. Would suggest keeping some 3mg on hand when you give the 0mg a shot. You might be surprised at what you're missing.

Depending on your tank/build, 3mg can deliver a good amount of nic. I've been trying to get down to 1.5mg, but find that as I go lower, I vape more volume. Might consider bumping my nic up some so I'm not vaping as much liquid throughout the day.