Can't go wrong with either. ABG is simple, quick, and fairly cheap (you can order it ready to go online). With the clay you have a little more work to do and may have to source the ingredients, and you can't always get them in the small quantities you may want to do a single tank (I bought my bentonite and redart in 50lb bags). I use both, clay with my obligates and thumbs, and ABG with my larger frogs.
Pat
Pat