It all depends on what you need and your budget. In terms of lab grade standard vs. gold, the main difference is that the gold package comes with the PM2 module plus lab grade conductivity probe and also lab grade ORP probes.
With the Lab grade standard you get temp and pH probes. So you will still need to purchase the ORP probe separately. And if you want to monitor Salinity, then you will need to get the PM2 module and the conductivity probe.
Knowing what I know now, I wouldn't bother to get the PM2 and salinity module. It's cool to track and report, but that's all. And some will also argue that ORP is a waste of time. So in a nutshell, the Standard version with long life temp probe and lab grade pH probe is what I recommend.
In terms of recommending a vendor, for online I recommend Bulk Reef Supply; I purchase almost everything from them. And for LFS I recommend Aquarium Village. They stock every piece of Apex equipment. In fact, I got all my Apex equipment from them.