Help interpreting site index results

[kpmcgee73]

Hi Patrick,

Hope all's well.

I'd really appreciate your help & sorry for the long thread.

Mainly I'm trying to get my head around interpreting the Google speed index score and how it correlates with other site metric scores.

Having read your link to information about Google's speed index score,

Q1. Am I correct in thinking Google's speed index score is the most important metric? Perceived site speed being most important?

However speed index scores doesn't always seem logical. I'll try to explain. I sometimes see results with a:

Low speed index score BUT with relatively slow / high general site metrics speeds
vs
High speed index score with relatively quick / low site metrics speeds

Some examples to illustrate below:

MY LIVE SITE RESULTS
Main mirror in Amsterdam, provided these results:

http://www.webpagetest.org/result/150814_GD_GCG/

Speed index: 1754
Start render: 1.628s
Visually complete: 7.000s
Doc complete: 4.683s

Most of these stats seem to be good. I understand a speed index score <2000 is good. But visually complete in 7 seconds doesn't seem good. I thought this would correlate with a higher speed index score.

However thinking about perceived experience, I can see the end user starts seeing the page begin to build at 1.6 seconds. Is seeing a page build early good perceived experience?

Q2. start render have more weight over visually complete times? Does this explain why the Google speed index score is a low 1754?

DEV SITE COMPARISION
When I test my dev site (cheap server setup) with a new Genesis WP theme all the stats seem better, some much better. But speed index 2641 is much higher, see test link below. I don't understand this.

http://www.webpagetest.org/result/150813_AZ_17DA/

I also repeated the test & got these freakishly good stats but the Google speed index score 1526 is only marginally better than my live site result.

Speed index: 1526
Start render: 0.611s
Visually complete: 2.300s
Doc complete: 0.861s

http://www.webpagetest.org/result/150814_XA_HH6/

Q3. So is the Google's speed index always accurate?

Q4. Which metric is most important when measuring perceived site speed? Is it (in order):

1. Google speed
2. TTFB
3. Start render
4. Visually complete
5. Document complete (load time)
6. Fully loaded

Q5. Is it normal for visually complete to always lag behind load time?

Thanks for looking.
Kevin