I haven't used used a Singer 306, but I can vouch for the 401. I picked one up off of Craigslist for fifty bucks, and it has been well worth it. So far I've easily sewn through nine layers of coated 1000d cordura. The 401 is one of the last household machines by Singer that is 100% gear driven. I've seen 'em go for between 100 and 200 bucks on ebay depending on the condition/attatchments.