I like to do both, and find that they complement each other with techniques. Trying to learn tricks, it's easier to do on fin or foil first then on the other.
For instance, I found getting into switch stance while planing a lot less intimidating at first on fin, and am now trying to add it on foil. I could enter it from a jibe by just staying in the front strap but it was something I wanted to immediately get out of. Sending it downwind and going fast is a lot less scary on fin than foil, and helps calibrate a bit for foil.
Jumping conditions are a lot easier to get for foil, but to me it's intimidating on a tall 103cm mast, a lot less so on a 72cm mast. I don't find them anywhere near as scary on fins but we don't get good conditions here on the regular. The guys that do them well here have 2-3x the years or more in the sport than I do. I figure with the TOW on foil I'll probably end up trying forwards at some point when I'm convinced I can jump reliably enough. Can I get the TOW with light wind to learn them with fins at all before trying on foil? Or will I try on foil first then on fin when it's finally windy enough for me to do it?
Honestly I'm stoked to see some good wingers show up here on days that I'm working on jibes, and they are jumping 10-15ft up, spinning, flipping around at high speed on 900cm2 wings, and it makes me want to be not a garbage lawn mower on a windfoil (which I pretty much am

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Same thought process with planing/flying 360s, helis, ducks, etc.
Jibes are way easier on foil, especially when the wind is not very strong or not even planable on fin, and that has given me a much better feel that bleeds over into fin. And nothing is quite like flying out of a jibe. Sometimes it still seems so far away for me on fin, but I know I can make it happen on foil (although unreliably).
The other side of it is some times, the wind direction and moon/sun cycles don't line up to be deep enough for foiling at a close spot, or strong enough for fin, so that makes the choice easy.
Now the main question is: if the tide is deep and the wind is strong, what to pick? At the end of the season here we had days with wind strong enough to plane on my smallest sail, a 4.4, so of course I chose fin, as then I knew I could make it out of the shore break alive in the biggest waves I've been in and not wreck my gear. Not quite there on foil yet, and other foilers in those conditions would be on more like 3.7s or maybe even smaller. But so far in real waves and strong wind I stick to fin. More than 2-4ft swells and <5.0 I start to feel over my head on foil very quickly.