Just looking up some numbers...
Sam Keller, 2007: 9 games, 63.1%, 14 TD, 10 INT (1 per 32.5 ATT), 133.74 efficiency
Tommy Armstrong, 2014 (Pelini): 13 games, 53.3%, 22 TD, 12 INT (1 per 28.75 ATT), 133.04 eff, 705 yds rushing
Tommy Armstrong, 2016 (Riley): 11 games, 51.4%, 14 TD, 8 INT (1 per 36.75 ATT), 123.92 eff, 512 yds rushing
Tanner Lee, 2017: 10 games, 57.2%, 18 TD, 13 INT (1 per 26.6 ATT), 128.5 eff
So yeah, in case anybody didn't notice, Lee throws a ton of picks, and his QB rating is no better than Armstrong's. Factoring in the rushing production, yeah, I'd take Tommy.