Depends on your flying patters. Star Gold has a lot more benefits than Star Silver - such as lounge access when flying anything but UA/US domestically. So if you spend a portion of your time overseas or even in Canada, going for the Gold might be a good option.

Upgrades are prioritized within status levels based on past year miles earned so since you are doing the challenge, you would be near the bottom of the upgrade tier in either case. My guess is that depending on the routes you fly, this could make a difference as for instance all the GPs might make the cut but only one or two SPs do - which would likely not be you based on your lower travel this year.