What are these silvery pumpkins

Steam has two major advantages:

Steam Sales

(edit: this is less true these days, other online stores now have huge discounts regularly too) 75% - 90% off most major titles within 6 - 12 months of release. There is nothing close to the deals steam have, not on online shops, not in bricks-and-mortar shops, not even second-hand.

Valve's reputation

Valve have proven time and time again over the years that they are "the good guys". They make a lot of effort to do right by their customers. So I trust them (more than any of the companies you listed) to not lock me out of my games if they can help it. If Valve ever got sold and decided to cancel Steam forever, they're the company most likely to secretly release a hack or something to keep my games running.

They are also extremely profitable, thanks to their excellent games (I mean the first party titles like HL, L4D and Portal), and to their excellent business model. They are the digital distribution company most likely to stay in business forever.

In hands of a good pilot Huey is pretty much indestructible if it keeps healing after a few cycles (they could even heal it right in the air). If I jump into one I would be dead in 10 seconds, but I still remember one guy that was murdering our whole team for the whole game scoring >4k points (and taking down choppers is my highest priority).

The best you can do is to spot it as early as possible and hope that a few teammates start helping, single handed you can only be somewhat an annoyance to a good pilot forcing him to go for a repair after couple cycles. To take cycle strafing armored chopper down in one cycle you probably would need at least 3 people with LMGs.

If I am the only one who tries to take it down, then the safest strategy against a good pilot is to shoot only when the chopper is turned backwards to you, and then quickly move to a new position before the next cycle. LMG seems to work the best.