Do Brittain's strengths - speed, perimeter, bh, pass,- outweigh the comparative deficiencies - ath, def, lp?

Name**********Yr.***Pos. A****SPD REB DE**BLK*LP***PE**BH***P***WE**ST**DU**FT***OVR
Glenn Brittain Sr. PG 34 73 13 32 4 39 96 81 78 50 83 92 C+ 70.1
Boyd Hirano Sr. PG 61 69 17 66 2 77 63 76 61 72 86 36 B- 66.4

I've been going with hirano based on defensive proficiency - but is Brittain's offense more potent?

I'd start Hirano, then have Brittain as your backup but high distro and +2 he's capable of scoring more, I'd up his distro more than what it is.

I don't think Brittain is good enough with such a low ath/def even if hidden in the zone

Which has been my general policy.

I *love* Brittain as a scorer off the bench and backup PG.  I'll take one or two of him every season.  I see your issue, though.  You don't really have a starting PG otherwise.  In the end, especially in a zone, I'd run him out there as the starting PG and hold my breath.  I suspect he'll be fine... but I wouldn't be happy having to make that decision.