There is no "better", they do different things. Alpha converts starches into sugars at mashing temperatures. Gluco converts complex sugars into fermentable sugars at room temperature. For all grain (or part grain) mashes I use both.
Using only Alpha will leave unfermentable sugars. These are desired for some types of beer (not American!

) but are of no use in distilling. Gluco finishes the job. You probably want both.
Chuck