well to start with in order for you to play around and get the overall lighting feel, lower you min and max a whole heap, bring em down to min 1, and max 20 for instance, that will help while tyring to set it up. once your’e there you can up them some to try and get that shadow detail back in there, don’t forget to up the samples relative to them too.
next is your sky affecting the gi like his is? because it doesn’t look like it is. make sure your sky is allowed to affect the gi you will see a marked improvement, possibly don’t use a sky but use a large sphere object too, this will speed things up some while trying to get the overall lighting.
you also don’t have to bounce that many time with the diffuse depth, bring it back down to 3 while you’re working on it.
how many lights in his scene? make sure you have the same, and in the same place.
then play around with the materials, in their illumination tab, under gi recieve and gi transmit. if you up the transmit factor then the light will bounce “further” without washing things out as much.
hope some of that helps.