Coming from a business perspective… because maybe I'm overthinking this...
Right now, Armstrong is 100% digital. It has to be because I can't afford to print copies and I'd rather share it with EVERYONE instead of the 3 people that would've paid for it had I charged money (my parents and probably one of my friends? Ok, 2 people then).
Its competition right now isn't necessarily against other digital comics though. Armstrong is free so it's competing for attention. It's not even really a competition between FREE webcomics, is it? I can say, "I'll spend money on this thing instead of that thing," but I'll hardly say "I'll look at this free thing instead of that free thing."
So it's a competition against Netflix, Hulu, Facebook, iPad games, etc. It's for your attention when you think, "What can I kill 20 minutes with on my lunch break?"
Also interesting to think about - DC and Marvel aren't competition to free webcomics - even digital DC and Marvel are no match for free and online comics. But free webcomics and digital distribution ARE competition for major comic companies which is why we have this knee jerk reaction (Wizard firing their entire staff without notice) from the industry.