@KPS Both APIs are completely different, the oldest one has never been intended for public consumption, it was developed for XO's internal needs even though we are not preventing anyone from using it 🙂
The REST API has been created exactly to address the need of a public API, use it if it covers your need.
Also, feel free to provide feedback and we'lll improve it.
Regarding the limit issue, it has been fixed 6 weeks ago, please make sure you are up to date.