I'd try 17m first. It's a great band that is not dominated by DX contests every other weekend during the winter, as 15 and 20 meters can be. I also find more activity on 17 than 15, and, although a bit less than 20 meters, the average station on 17m seems to be running less power and smaller antennas than you find on 20, so it's easier to "compete."
Also: The band that's the "most open" at any given moment is the band that's closest to the m.u.f. Currently, the m.u.f. is running around 30-40 MHz during the day, which would favor 10 meters, but settles down to around 20 MHz for several hours in the evenings, which would favor 17 meters, exactly. Which probably explains why, when I tune around from 10 meters through 40 meters (and all bands between) when I get home from work at about 0100 UTC, the strongest signals are on 17m, and it remains that way for hours.
If this is the time of day you like to operate, and you want to be as competitive as possible with a small antenna, I think 17m would be the band. For low-power CW/digital only, and nighttime operations only, I'd recommend 30m instead; however you mentioned SSB, and that's not allowed on 30m.
73 de Steve, WB2WIK/6