The AL is ash and the silo is alder. Both come with maple necks, and the Silo Spec can be ordered with a RW board. To my understanding the regular SSS Al cannot be ordered with a RW finger board.
Seeing that both Ash and Alder have been in the lineage (and still are) for strats, I wouldn't say that the tone wood is the definitive factor in that strat like tone. The Al and the Silo both use the two point vintage trem system or body-through hardtail design. I have a SSS Silo Spec, and have played an SSS Al extensively, and I'd say that the AL is more strat like, and due in large part to the custom Seymour Duncan pickups.
A couple buddies of mine, and many knuckleheads have changed pups on a SSS Silo Spec, from CS '69s or Texas Specials, Suhr MLs, Lollar Blondes, or Fralin Blues, with outstanding results.
Stock vs. Stock the Al gets there more, but after changing the pups, who knows?
I'd recommend playing both if you can and see which you like more stock, then go from there. The custom single dimarzios on the Silo Spec are definitely NOT what you'd call vintage 50's- early 70's strat tone, but they're quite nice, I like em personally and still use em.
If a rosewood board, or a humbucker in the bridge is a must for you, then the Silo Spec would definitely be the way to go.