Based on the specs alone, I'd choose the Polk over the DefTech:
- The PSW10 is rated at 50W RMS, while the DefTech is rated at 150 "mystery" watts. Given DefTech's penchant for playing "fast and loose" with specs, the rating is probably the dynamic wattage, which would place the RMS wattage rating quite a bit lower.
- Similarly, I suspect the DefTech does not extend down to 24Hz @ -3dB (more likely @ -6dB or even -10dB), while the Polk's 35Hz extension is likely @ -3dB.
I haven't heard the DefTech, but I have heard the Polk and I think it would be a decent sub for a modest system in a smaller room.
That being said, if you can stretch your budget a bit I think you'd be quite a bit better off with the Energy S10.3 for ~$200 when on sale.