Which scenario sounds best.
1. Still at PCL in 5 years. Upside, no commuting. Downside, uncertain future.
2. Going to Spirit. Upside, career advancement. Downside, commuting. Not your "destination career airline." Could hang out here till Delta calls.

Me personally, I'd go to Spirit and wait for Delta (if that's what you want long term). You may end up liking Spirit enough to stay, or if not, it's still a better bet long term than PNCL.