Ok, just out of curiostity I just did a test, a cold boot.

Two machines:
- 2009 Acer Aspire 7535 (AMD Athlon X2 QL-64) laptop running build 10074 of "Windows 10 Pro Inside Preview" against 
- Mid 2012 Macbook Pro (2,3 GHz Intel Core i7), running Yosemite 10.10.3

I already know which one I prefer (and it is not going to change, whatever the results), but I do run into this:

Acer 2009, W10 preview      MBP 20122, Yosemite 10.01.3
0:11      Logo is displayed   Blank screen
0:19     Logo displayed
0:23 Login screen displayed   Progress bar starts
  Slow typing on my part    
0:58 Logged in   Progress bar 30%
1:30     Login screen is shown


PS, I know... a clean install always boots faster regardless the OS