It’s all relative of effort, in comparison with the teams involved in the battle. If long term coach preference is the only preference and the battle is between two equal teams in every area (prestige, effort, and other preference scores), then it’s going to be very helpful in getting you up to the leader in the roll.
but if things aren’t equal then it just becomes another part of the overall recruiting score. As far as it’s strength in comparison to other preferences, I rate long term coach as just behind wants to play, wants success, and distance. But a lot stronger than every other preference not mentioned