The difference is you can take the console with you to a friends house for example and just plug it in to play your games.
Or you can take it with you when you're on a trip and play at the hotel for example.
If you want to play deus ex on a netbook it would be possible also because they scale the game down. It depends on your available bandwidth.
Even on steam you don't own the game. You're paying to license the game. That's why they call it a subscriber agreement and why they can lock your account and take away all your games if you happen to cheat in one.
2. LICENSES
A. License Terms.
Steam and your Subscription(s) require the automatic download and installation of software and other content and updates onto your computer ("Software"). You may not use the Software for any purpose other than the permitted access to Steam and your Subscriptions. You understand that for reasons that include, without limitation, system security, stability, and multiplayer interoperability, Steam may need to automatically update, pre-load, create new versions or otherwise enhance the Software and accordingly, the system requirements to use the Software may change over time. You understand that neither this Agreement nor the terms associated with a particular Subscription entitles you to future updates, new versions or other enhancements of the Software associated with a particular Subscription although Valve may choose to provide such updates, etc. in its sole discretion.
Valve hereby grants, and you accept, a limited, terminable, non-exclusive license and right to use the Software for your personal use in accordance with this Agreement and the Subscription Terms.
The Software is licensed, not sold. Your license confers no title or ownership in the Software.
Additionally, Valve hereby grants, and you accept, a limited, terminable, non-exclusive license (the “Installer License ”
to reproduce and distribute an unlimited number of exact copies of the Steam client installation software ("Steam Installer") via online download; provided that the following conditions are met:
(i) you must redistribute the Steam Installer in its entirety;
(ii) you must not modify the Steam Installer in any way nor integrate or combine it with another software program;
(iii) you must redistribute the Steam Installer on a non-commercial basis (i.e. you may not charge any fee or receive any compensation for your redistribution);
(iv) you must include any Valve license agreement provided with the Steam Installer; and
(v) you must preserve in all copies of the Steam Installer all copyright and legal notices that are attached to the copy of the Steam Installer received by you.
This is a good deal for the target audience I mentioned above because the console is going for at least $30 on ebay.