Scan Count of a query increased from 1 to 2,226 after creating a non-clustered index
First scenario, it's scanning the whole table and looking through 14553 pages of data. Second scenario, it's doing 2266 seeks (but counted as range scans) which each look at just 2 pages. So the second one is way better. Plus, many of those seeks will probably be looking at pages which have just been looked at, so on a cold cache it will be an even larger performance benefit. And, the second is more likely to parallelise better, being lots of small operations rather than a large one (which could still be parallelised, but it's more effort).