Thrift used to support more languages (this has changed). gRPC was more performant (take w/ grain of salt, this is word of mouth) for a while -- unclear if it's changed or if the difference was ever that significant except at very high scale.

I think they're pretty similar and you can't lose either way. Facebook's support of Thrift and Google's of gRPC make both decent options.

One thing I will say about gRPC is that it plays nice with Google's build system (Bazel) and some Google APIs now have first-class gRPC support. If you choose thrift in your stack you'll have to call APIs using JSON or support gRPC anyway if you want to use them for those API calls...so gRPC might be an attractive choice. Furthermore gRPC's go interop is also excellent if you happen to be a fan of golang.

I've used Thrift on a project in the past and one feature gRPC has that Thrift doesn't is the ability to use streaming semantics. This would have actually been very useful for the project I used Thrift on. If I were implementing it now I'd definitely use gRPC.