I think it's close, but I'd stick with Semin here if you're looking for the home run. The guy looks motivated, is playing for his next deal, and in that scenario is still one of the higher-end offensive talents in the league. Towes is no slouch and should be more consistent, but Semin definitely has the chance for a higher point output given that his entire role with the Canes revolves around adding offense whereas Toews is relied upon for much more than putting up points.
14 Team H2H Dynasty League (14 keepers, no farm)
Weekly Starts (3C, 5W, 5D, 1Util, 2G)
G, A, PPP, SOG, BS, +/-, GAA, W+OTL, SV%
C: MacKinnon/Eichel/Kopitar//Pinto/Wright
W: Ovechkin/Toffoli/Necas/Giroux/E.Kane/K.Johnson(IR)/Schmaltz/Bjorkstrand/Drouin
D: Dobson/Trouba(IR)/Mintyukov/Gostisbehere/Martinez/Edvinsson/York/Gudas(IR)/Tanev
G: Saros/Demko(IR)/Askarov/DeSmith