Depends whether you think Player of the Season is to reward the best player on the team, or the player that's done the most to capture the hearts and minds of the fans. I think they're only occasionally the same thing.
If it's the former, I'd say it's probably Nelson.
If it's the latter, I'd say it's probably Ruffels (been with us the longest, multiple positions, consistency and the last minute winners...…)
If you want to combine the two, you can probably come up with a convincing argument for Brannagan. Certainly hoping he's still with us next year.