Ignoring BB's evident belief in Stidham, sure. If BB brings on Dalton, you are right. If he doesn't, you are wrong. It's not credible that BB's proprietary knowledge of Stidham from coaching him for a year is meaningless.
I mean, whether Stidham turns out to be a better or worse quarterback than Dalton seems to me a question independent of whether Belichick has faith in him or not. Would I put money on Stidham starting 10 seasons, going to the Pro Bowl three times, and finishing those 10 seasons with a winning record and over 200 touchdowns? No, I would not. Nor would I make a bet at even money that Stidham would outperform Dalton next year if you could play some parallel season with both as quarterback of the Patriots.
Any belief in Stidham is pure religion (Belichick must like him, so he must be good) but historically the probability of a 4th rounder being a good quarterback is not very high. Ryan Finley and Will Grier were drafted higher than Stidham last year and were both putrid.
Going back to 1990 and excluding this and last year, there were 259 QBs drafted in round 3 or later. Of those, the following were 'acceptable' starters for some period of time:
1. Neil O'Donnell
2. Brad Johnson
3. Mark Brunell
4. Gus Frerotte
5. Matt Hasselbeck
6. Marc Bulger
7. Tom Brady
8. Josh McCown
9. David Garrard
10. Matt Schaub
11. Kyle Orton
12. Matt Cassel
13. Ryan Fitzpatrick
14. Tyrod Taylor
15. Russell Wilson
16. Nick Foles
17. Kirk Cousins
18. Dak Prescott
19. Jacoby Brissett
Note that many of those guys weren't all that good, you never really feel comfortable with a Kyle Orton or Jacoby Brissett or Ryan Fitzpatrick as your starter, but that's a 7.3% success rate in finding an acceptable starter. Cut down the list to above average or better starters, guys I'd absolutely take over Dalton (i.e. Brunell, Hasselbeck, Brady, Wilson, Cousins, Prescott) - you're at a 2.3% success rate.
There were a couple undrafted guys in this timeframe (Warner, Romo, Delhomme, Garcia, Fiedler, and Hoyer being notable names) that you could add but it still doesn't do much to move the needle considering there have been hundreds of undrafted QBs.