Consistency is, arguably, the most important thing in any competitive deck, and for me this is what makes Silhouette's 40 card deck minimum so attractive. At the time of writing, the only Runner with the same out of the box consistency is Chaos Theory: Wünderkind, and +1 isn't as much fun as peeking at an unrezzed piece of ICE before you face-check a remote.
Time for a bit of maths. Pick a card, any card that you consider a must-have card to get your deck going - Magnum Opus drives my economy, so I'll use that as an example, but it could be anything. My ideal first turn might be to drop Magnum Opus #1, and then for 6 . If I put 2 x Magnum Opus in the deck, that's a 1/20 chance of drawing it first card, with increasing odds as I draw more cards and the deck gets smaller. With a 5 card starting hand, that's better than 1/4 odds of Magnum Opus being in my opening hand, and me playing my perfect first turn. The option to mulligan increases those odds to (roughly) 1/2, meaning that every other game my opening turn could be exactly the same.
For those games when you don't beat the odds, a 40 card deck isn't too difficult to dig through - Quality Time is a cheap splash, but it encourages you to overdraw, and the last thing you want to be doing with such a small deck is discarding cards. For that reason, I prefer Earthrise Hotel - the drip style draw gives you more time to get cards out of your grip and onto the table.
It's probably not a good idea to over rely on a single card for your economy, but you get the idea - out of the box (and ignoring cards like Paige Piper) a 40 card deck is significantly more reliable than a 45 card alternative.
Silhouette's actual ID ability lends itself towards a cautious approach, and has excellent synergy with Security Testing, Feint, and Quest Completed. Just like when facing against other Criminal's, the Corp is likely to ICE up HQ pretty strong, so the central focused breakers (Breach, Alias, Passport) are worth considering.
As I mentioned, discarding cards isn't something you really want to do with Silhouette - so caution is key. There isn't a lot of room for recursion, and you are probably only going to play with 2 copies of any given card, so even the smallest amount of net or meat damage can ruin your day. Install critical software and hardware as soon as you draw it - these cards are much harder to trash once they are on the table. Also, consider Film Critic for disarming Jinteki: Personal Evolution and Argus Security: Protection Guaranteed, and, of course, Plascrete Carapace for surviving Scorched Earth.