They are very different, it's been seven years of heavy development since forking. For comparison that's longer than the time between apple forking kHTML to make webkit and the the first release of chrome.

The passage of time alone does not make changes.

The question was: What are the differences?

Start Safari and Chrome on a mac, open several tabs and observe:

- Memory usage

- Energy usage

Then open https://browserbench.org and do the benchmarks.

Webkit will dominate Blink (and for that matter Gecko) in all categories.

The question was "How different are Blink and WebKit these days?" and "But perhaps that has changed?".

My answer was "they are different" and implicitly "yes", partially because of the heavy development work that has been done since the fork seven years ago.

If you look at the featuresets and when they introduce features I think it's reasonable to conclude they have diverged enough that they can't just pull patches from each other.

Also, there was a webkit mailing thread back when they introduced their cut-down version of service-worker that said that most of the code from blink was basically unusable for them because of the differences.