Pro: The 78 will be easy to get to. The site is close to the Roosevelt subway station that serves the Red, Orange, and Green Lines, and it's accessible from downtown, interstates 90 and 94, and Lake Shore Drive. There may even be water taxi access via the Chicago River. If a new stadium is built there, it will be easy to get to via public transit and car -- and by foot from a few neighborhoods, such as the Loop and South Loop. There will likely be plenty of space for parking, as well.
Con: The current stadium is already easy to get to, so that's not really a reason to move. The Red Line drops fans off a block or so from the stadium, and Green Line and Metra stops are within walking distance. The park backs up to the Dan Ryan Expressway, providing easy access for fans arriving by car. There's plentiful parking.
Pro: A stadium surrounded by retail can cap off the ongoing development of the South Loop. The neighborhood has been hot in recent years, with gleaming apartment buildings and condominium complexes popping up. The proximity to the Loop, the Museum Campus, and Soldier Field is a plus, too. A developed 78 with an attractive new baseball stadium as its centerpiece could turn an ugly parcel of mostly undeveloped land near Chicago's downtown into the newest "hot" area of town.
Con: Leaving Bridgeport, the neighborhood surrounding Guaranteed Rate Field, could leave emotional and economic scars. I am sure not every local likes having the inconvenience of 81 home games every summer, but I am sure some folks like living near the stadium. A few bars such as Turtle's and Cork and Kerry at the Park seem to rely on Sox fans to stay in business. There's also at least one sports memorabilia store that likely depends on Sox-related foot traffic.
And while it likely has little to do with the stadium, the once-forlorn area immediately across the Dan Ryan has been improving in terms of available retail and public safety over the past 10-20 years. Will a Sox move hurt certain businesses? Will Bridgeport residents feel a loss of pride over the team packing up? Or will they be glad to see traffic dip on game days?