They are similar in many ways. It depends on what you want to vanish. Nick covers a lot in the download for the Raven that makes it very versatile.
In my eyes I think that the Raven is more practical and a tad more visaul. You cannot do the vanish in the spectator's hand quite as cleanly with the Gecko. Also, the four-coin production and vanish Nick does in the trailer can only be done with the Raven.
The Raven's reset is also faster. You could vanish items back to back with the raven as well which cannot be done with a Gecko.
Honestly, when it comes to the Gecko I'd rather use a Topit to vanish some of the larger items. Retrieval is easier with a Topit vs a Gecko. And, they both require a jacket anyways.
For smaller objects, I'd go with the Raven.