SkyTeam is more popular in Europe? Compared to what?
While Sky Team may be more popular in France, The Netherlands, The Czech Republic, and Russia, many in Europe - as well as those who travel to Europe quite a bit prefer Star Alliance. I don't know how one can beet the combination of A3, JP, LH, LO, LX, OS, OU, SK, SN, TK, TP. Or think about it in terms of European hubs. Skyteam has CDG, AMS, MAD, MOW, OTP, & MOW. Star Alliance has:
A3: ATH with focus cities at SKG & LCA
JP: LJU
LH: FRA, MUC, & DUS
LO: WAW with focus city at KRK
LX: ZRH & GVA with focus city at BSL
OS: VIE
OU: ZAG with focus cities at DBV & SPU
SK: CPH, ARN, & OSL
SN: BRU
TK: IST & SAW
TP: LIS & OPO
And don't forget, it is very difficult to actually find award seats with DL & AF's plan. Perhaps on another Sky Team airline, but not DL or AF. I'd stick with *A -- or consider, possibly, OneWorld.