I have reasons for supporting Valve and disliking EA and here are my reasons: (yes its a wall of text, i'd imagine i'm going to get a lot of TL;DR)
First and foremost the treatment of customers. This is a very broad topic so there are a few aspects that go into it. EA has banned people because people have openly talked *badly about them. so terms of service were violated, so they had a 'legal' ability to do so, and thus because a customer was clearly dissatisfied with EA, EA revokes their ability to play the games that they bought. Ok, technically you buy the right to play the game, not the game itself. this is with any program, game or not. On the other hand, when people "talk badly" about Valve, Valve may take the dissatisfaction into account and try and do something about it.
Accessibility is another point under the treatment of customers point. And not accessibility on a game level. In every single one of Valve's games sense 2004, Gabe openly gives his email address and encourages players to send their responses directly to him. Many cases (not all) he has replied back to the senders. The ability for customers to have a direct line of communication to the CEO of a company, to say whatever they want, positive or negative, is something that i see extremely rarely and something that, although i may not use it, i value as a customer. Correct me if i'm wrong but that level of communication is nowhere near present with EA.
Next, Valve is a privately owned company. EA is not. EA has to keep shareholders happy, regardless of how much these shareholders care about games, quality of games, or how customers are treated, as long as there is a profit. Valve can and does take liberties that EA could not do. Valve has shut down the entire production of developing games, to take a few months off and do entirely in house experimentation, trying to come up with new things with no guarantee that anything positive would come out of it. Why? because of the possibility of coming up with something so different, new and fun for their customers rather than sticking to the same old formula. I will give EA credit in the past they have done a lot of good things, regardless of how i personally feel about them they are in a very strong position in the gaming industry, and they had to do something right to get there. But recently i have felt (though i could not prove it) that EA has settled because of shareholders not willing to take risks.
And then the trivial matters. I have a rather decent size library of games on PC, roughly 90-100 games. of that all but maybe 6 that ive bought retail are on steam. i bought most of them on sale, and you know, its been pretty simple, they are all in the same place. my entire library is on steam. call me lazy and i'll accept that, but i really don't like the idea of downloading another third party software to have a small set of other games on. I would much rather keep them all in the same place.
To be honest, i have not touched Origin. i have never used it, never downloaded it. My argument is not which is better Steam or Origin, my argument is that i prefer one company over another. Thus, i will support Valve and Steam over EA and Origin. As a customer, the best way to support a company is to use their products, and so, I use steam and i have not used Origin.
Then you go on to say what if Valve changes their methods. To that i respond, as of now, i am still in support towards what Valve is doing. Yes valve can very well change their policy, probably even more easily than EA can. If it were to change to something that i dont like i would probably email them addressing my concern, and depending on the situation yes, i would be less supportive of valve. i would hesitate before buying from them. That is the entire reason why i hesitate to use somethign from EA, I didnt have a problem with them a while ago, now i do. and thus i show my lack of support. The point though is that while valve can change, they have not. that is why i support Valve, and use steam