how good is it compared to the non-light version for only ad blocking?

It has a preset few lists in the extension, and you can only adjust a slider to determine blocking level, with the default just being DeclarativeWebRequest (non-blocking) ad domain blocking, and the higher tiers I suppose blocking dynamic content on the page like usual. No custom filters.

When it was announced I used it for a while and I seem to remember that the lack of cosmetic filtering was the only thing I really noticed.