notice, by VR, its could also be VR phoenixes to counter VR and lift off immortals.
another possibility in PvP is that if 1 side held of korean 4 gates without 2 gates rush, 4 korean can still come up ahead early on with the wrap gate speed production while the other side a little slower but has more probe for long run. this normally result robo counter 4 gates or 4 gates vs 4 gates. if robo, there will be lots of sentries to turtle into colossi tech, else 4 gates vs 4 gates there will be lots of zealots and the gas go into DTs and 1 side will suffer and get forge, hope to roll over with +1 timing
sneaky expo early in this situation is almost a 50/50 since if you scout the enemy going colossi, there is no way you can counter it unless u having 1 yourself.
things so crucial in this match up is:
1/ heavy zealots army 90% wins vs heavy stalkers early on.
2/ VR are being use as the "evolution counter" from the old trend which is 1 base colossi. we can wrap things up with 4 gates > VR > colossi> 4gates atm.
3/ VR can deal way more damage vs any type of build if they are correctly used/micro. the advantage of air tech is HUGE with the ability of constant harras pressure and gaining map control.
4/ on some certain map like steppes, there are some unique style to play the game such as 2 gates wall nature PvZ style. you 2 gates zealots until wrap tech queue up, expan and get lots of sentries out to FF hold the push. => colossi
5/ getting obs is a good way to garther information but the cost is not only 50 100 1 supply, it also cost you time to get 1 immortal out fast. lots of time games could be lose by a small decision like that.
6/ most effective upgrade would be shield instead of + 1 attack due to the fact that the army composition now is VR+ zealots + sentries. but shield are WAY more expensive and take time to get.
more update about Protoss will be on my blog so make sure to check it out =)
edit: i am not responsible if you think this belong to strategy, it simply just some personal thought and has no one confirm what is right and what is wrong. if you have read my blog entries, those are just "thoughts" of a Toss user. However, you have the right to think about my thought, correct, improve it and make it into strategy. Notice how did i simplified at least 30 possible situations that can happen in current PvP just in 4 paragraphs. In real, its much faster and complicated so i just want to throw it out for you to compare this to your games and see what did you do wrong =).... GLHF folks
+ fast expanding is not "impossible" if its a 4 players map. simply you will spend 400 mineral on a HIDDEN expo and use the gas on sentries for FF. FE is normally follow by air tech to force enemy to delay robo tech which can potentially break FF. Air tech also requires the enemy to keep stalkers count as high (aka. no gas for fast DTs) and IN THEIR BASE in stead of pushing out with the risk of VRs killing mineral line. If your micro is not good enough to keep VRs number high (2-3 at least), suggesting you to get a forge and cannon ramp. this will make sure no DTs gatting in and provide some fire power when come with FF (its not a bad choice since you are spending most of your gas on sentries anyway forge and cannon will burn your mineral down a little bit)