Both scopes are about FR5 so that's 1000mm vs 1500mm.
The Nagler 17 has 82° AFoV, that SW28 56°(?).
1000mm/28mm=35.7x and 56°/37.7=1.48° TFoV
1500mm/17mm=88.2x and 82°/88.2=0.93° TFoV
a 25mm 100° eyepiece (ES) in the 12" would give you about the same TFoV (object framing), but part of the field would be peripheral vision.
Have you taken the parameters to Stelvision or Telescopium?
You could take screenshots and paste them side by side in post to compare.
Do you not reach for the 12mm very often because of bad seeing or are you not into higher powers observing?
In that case, and for the purpose of outreach, my choice might be the Panoptic 35. I find it very comfortble and when barlowed is like a 17.5mm.
Or consider a cheaper alternative for outreach.