Shop applied fireproofing applications are done in a more controlled environment. This can result in a better product. It also arrives to the jobsite coated and ready for erection. This can help shorten the critical path by not shutting down other trades during field applied fireproofing.
Dependent on your field labor costs, shop applied fireproofing might be a more economical choice. Field labor rates are typically higher than shop labor rates. While intumescent coatings themselves cost more, the labor savings can offset that.