Of course, I am talking about when Instant Search is disabled.
Quite a while ago, Google certainly did differentiate between "Enter" vs. Click. And, according to Google, "Click"ing was recommended.
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No there is no way that the developers at google would include this what possible functionality does that serve? If anything it would reduce functionality by making certain searches more difficult to find when using one method vs the other. Google uses a specific algorithm determine their results why would they create separate ones for two two events which trigger the same thing, your results.
Something which may be of interest to you: http://en.wikipedia.org/wiki/PageRank