[robwormald]

That's discussed in the doc (and there's some metrics). Update speed takes a (minimal) performance hit, in exchange for code size reductions.

We (and our colleagues at Google working on the web in general) find that the largest impact on performance comes from simply shipping less code.

Edit: correction: turns out our tests show we didn't take a perf hit on updates at all, and in fact ever-so-slightly improved. So win win :D