Just some random thoughts, I'm sure others will chime in

Pro SWA:
SWA has never furloughed, been profitable almost every quarter in the past decade, largest carrier of domestic passengers in the US, one of the best financial balance sheets of any airline, greatest company culture/management, always one of the top places to work in the country (not just against airlines), great payscale/benefits

Con SWA:
SWA would have closed the DEN base and pilots there would have to commute. Airbuses (Airbii?) would have been retired, Lynx (the Q400 regional subsidiary of F9) would have been sold off or somehow eliminated, staple to the bottom of the SWA list means crappy QOL, being purchased means F9 brand dies.

Pro Republic:
Up and comer airline with a super low cost structure trying to get into the low cost carrier game. Ambitious management, F9 will be one of the flagship pieces of the Republic company. DEN will remain a fortress hub, F9 employees will retain their jobs, opportunities for expansion and new crew bases, F9 has been a thorn in the side of SWA in DEN and could be a real threat in the future to SWA and the rest of the LCCs in general.

Con Republic:
Super low costs are going to be a priority, payscales in danger. Keeping F9 seniority list separate opens the threat of whipsaw using the other Republic pilots against the F9 pilots for concessions, seniority list integration could be very ugly. Unproven leadership in a very tough economic time. Growth might force junior pilots to commute to new bases.