I'm towing a manual transmission Honda Fit. 2012, so it could have been an automatic. I like the amount of space and flexibility. 2-3 people and huge cargo space, 4 people with luggage for 3 (including the toddler), 5 people with a couple suitcases or lots of groceries. 35 mpg average over the past 3 1/2 years, 40+ on highway trips with just me. Almost enough power to be fun to drive, but tempted by Focus ST which has twice the HP but only gets 22 MPG (my brother bought one, I'm jealous how much fun it is to drive a manual transmission compact with about 12 pounds/horsepower instead of 20 pounds/hp).
Just what are you seeking in a subcompact/compact? Performance, economy, space, fun, low cost? There are lots of choices out there, and most of the manual transmission models are towable. Almost anything is a step up from a Sonic.
I don't expect to trade the Fit before 250,000 miles. The 1999 CR-V I bought for my daughter went 297,000 before the engine blew an oil seal, my SIL was disappointed about not getting to 300K. Your Sonic might be good for another 10 years, if Daewoo builds cars as well as Honda does. I know they make good fishing reels.