Technically slightly slower because offset value needs to be retrieved from provided member name, but the look up (hashtable) is very fast. Difference is trivial.
The advantages of the new natives are mainly:
- No more hard-coded offset value in plugin. If for some reasons value would change, you won't need to update your plugin. Only gamedata will need an update, and it's planned to have an auto-updater similar to Sourcemod.
- Much safer. Since type/size are hard-coded in gamedata, we have more sanity checks. This should greatly reduce any wrong usage and therefore potential crash.
- It supports also more type and kind of increase readability since you have to use the real names now.
You would want to use _pdata natives if your mod is not supported (currently only CS/CZ, DoD, HLDM, OP4, and TFC).
I don't really see others contexts where it would be still needed.