Zapier is more advanced (and user friendly) and more towards business systems/community. IFTTT is geared more towards private consumers and also, the integrations slant more towards home automation, internet of things and so on.
Both of them cover all the typical systems though. But Zapier has more triggers and actions.
Also, a VERY IMPORTANT advantage of Zapier and an example of “more advanced” is that it is able to forward source URLS for systems like GMail and Evernote - contrary to IFTTT.
This means that if forwarding a GMail (e.g. by tagging it), one can insert a back-link in the text/comment as well. Same goes for Evernote.
This makes a HUGE DIFFERENCE in these cases where users want to connect systems and workflows. Like Matt_Groth also mentioning he wanted to forward mails from Inbox(GMail) and want to refer to them later.
Also, I believe this backlink feature makes such an integration more likely to replace or take the pressure off the demand for other integrations, such as the one for Evernote already listed.
Since users would be able to mark a note there and have it show up in DL with a URL in the text/comment if so desired. Not as advanced as a “hard link” but it goes a LONG way.
And of course, at the same time it opens up connections with 750+ other systems and webservices in one go.
My vote is for Zapier because of the backlink feature mentioned, to tie in my Gmail for project correspondence, my Evernote and my Gdrive/Dropbox for linked project support- and reference material.
But FOR SURE I will also cheer for an IFTTT solution is that is the choice. It will still be a major advantage. Even the email receipt would be a great advantage (but IFTTT or Zapier would make it up for export / email sending as well. Not only receipt).
It is the lack of all this in WorkFlowy that caused me to look for alternatives and thus find DynaList. WF seems stagnant but DL is alive and moving and this gives me hope for it to show up here.
About Zapier, the premium version is paid, but the free version is also workable for limited amounts of traffic. (Plus, you can set up several dummy accounts to spread out the load. This is very easy, especially now that some browsers like Chrome also support several browser profiles open concurrently. I have a couple of separate profiles with separate Gmail addresses that I just open and use for this kind of “system management”. Each Zapier account can connect to any other system accounts, also other Gmails).