What are your priorities for the new sail? Choosing Dacron would suggest price and longetivity are key factors, but the resin coating has an impact on both those items that could eliminate the cost/performance benefits.
Something like Dimension's SF260HTP could make a great sail, but I wouldn't use such a firm finish woven cloth for the mainsail due to the handling requirements of the material.
Since the mast extrusion will only accept flat slides, there's no simple way to convert to boltrope. Instead, you'd have to remove the slide stop and feed/remove the slides each time you raise/lower the sail. Even temporarily allowing the cloth to flake as it's lowered would break down the coating rapidly - the material's very crisp! And our booms are so high above the deck that it could be a struggle to contain the sail when it's in transition.
I'd suggest the same cloth, but without the HTP plus firm finish, would be the best practical high performance choice for a Dacron mainsail. Another alternative would be the newer woven cloths suitable for triradial construction, but their durability has not yet been proven and attempts to develop similar cloths in the past were not very successful (I speak from personal experience on that subject!).
FYI, in general a mainsail made of firm finish should be priced about halfway between an entry medium quality dacron and a crosscut Kevlar laminate sail, and about the same price as a crosscut Pentex laminate sail.
Sail purchase decisions can become quite complicated with so many options but I'd explore other performance alternatives.
1976 MkIII #632