Depends: which is more precious: network bandwidth, or my development time.
High volume: custom-binary wins, just like you said. Low volume: REST/text wins.
There's something to be said for being able to try out your API in a web browser in 2 minutes. Compression also goes a way in reducing the volume of text, though not the latency of follow up queries that are too finely granular.
Small, sharp, tools swapping text is very unixy. Even if sometimes the response is a binary document :-)
High volume: custom-binary wins, just like you said. Low volume: REST/text wins.
There's something to be said for being able to try out your API in a web browser in 2 minutes. Compression also goes a way in reducing the volume of text, though not the latency of follow up queries that are too finely granular.
Small, sharp, tools swapping text is very unixy. Even if sometimes the response is a binary document :-)