The SRD doesn't have 4th edition.
Anyhow, the SRD is a cool concept, and one I used plenty.. but in the long run, it's just a pale, pale comparison. DDI does more, it's configurable, and it builds stat blocks out of not only the standard sources, but also out of every monster in an LFR module, Dragon, and every Dungeon adventure.
And anyhow, that's only a single tool compared to the archives of Dungeon and Dragon material. PLUS the monster builder, the bonus tools, character builder, the Rules Compendium (not sure how I ever lived without this kind of tool, really), Plus all the other stuff.