I'm considering the same thing for my next SPT payout on my original account. Converting to DEC is better in the short run but I'm never going to leave that DEC lying around. I'd start trading with it, which is hopefully profitable as well, but collection value is much lower in airdrop points.
AND the aidrop lasts 1 year. Staking the SPT means, you're going to snowball it into even more SPT and airdrop points. Also depends on the APR of SPT. I'm gonna have to do some research and turn it into a post, I guess. :)
RE: Splintertalk: To SPT or Not To STP? (How To 3x Airdrop Points)