They are both VERY good effects; however they have completely different performing requirements (not even counting the gimmick used for CoinOne).
In 3 Fly the hands are held at chest height with your spectators at least arms length away looking mainly
up at your hands and face. With CoinOne (or even 'The Deep' from Out of Control / Totally Out of Control) your spectator is standing next to you looking
down at your hands.
While you can perform 3 fly for a whole crowd of people (at all different distances away from you) CoinOne is often better for a single spectator very close to you.
In my opinion you may want to ask yourself, "How do I usually perform?" Is it most often for a crowd of people (like when performing a magic show, birthday party, etc.) or is it mainly one-on-one (table hopping, walk-around, etc.)?
If you are a "hopper" then you may get a lot of mileage out of the "visual" walk through found on the CoinOne DVD. If you find that you like the effect enough to take the time to master it, you will become obsessed with deep backclip work (as I have) and it will naturally lead you to other uses, effects, applications ...and purchases. (I recently picked up David Roth's "Expert Coin Magic" just for the deep backclip work, and New York Coin Seminar Volume 4, just for Geoff Latta's deep backclip copper silver routine.) When performed correctly, routines of this nature are VERY deceptive and Homer's CoinOne is one of the best places to get started on this work.
If you perform more often for groups, then learning some variation of 3 Fly may be more rewarding. Don't be disappointed though when you purchase Chris Kenner's book and notice that 3 Fly isn't in there, it *IS* there, but it is called "Menage et trois" instead of 3 Fly. Both Daryl and R. Paul Wilson have less technical versions. Daryl's is sold under the name "3 Fly III" and comes with a DVD and colored dollar sized poker chips to aid learning. Paul's has been called Scottish Fly, Crowded Coins, or more recently Completely Crowded. Not a bad price either for Paul's (only $10) from his web site here:
http://www.rpaulwilson.com/circleofconfidence2.htm
...learning
any 3 Fly routine will eventually lead you to the work of Chris Kenner, Gary Kurtz, Troy Hooser and of course John Ramsay.
Okay, so having said all of that. Buy Kenner and Liwag's book! You will get the original source of 3 Fly and the Sybil cut, as well as "The Deep" (which is also on the CoinOne DVD) in addition to some other real gems (like the Magician slayer called "Twin Peaks" for example) which are hiding in that book.
Hope this information helps,
-ThisOneGoesTo11
