@Mordenthal
As Korebian says, you'll need to know your approximate SEP values, which widely ranges with gear setup. However, the numbers Korebian posts I would argue are not to be taken as guidelines at all, since for example his hit weighs more than strength, suggesting he's not hit capped or accidentally included negative deltas when calculating SEP values (which is included by default). Expertise does not fluctuate that much either in the sense that it's never worth losing expertise for any other stat if you're not softcapped. The reason expertise SEP values seems to fluctuate alot when you're close to the cap is that Simc by default calculates stats in increments of 300 rating (I believe), which if you're slightly under the cap can put you over by quite a large margin which deflates its value, which makes it appear to be a weaker stat sometimes, and other times a very powerful stat. The truth is it's always powerful as long as you're not softcapped (26 exp), no matter what value Simc gives you.
Now to socket bonuses, once you got your SEP values it is straightforward and easily explained. You want to compare the sum of the gem's stats (
[Design: Inscribed Ember Topaz] or
[Design: Etched Demonseye]) + the socket bonus versus vs a pure
[Bold Inferno Ruby]. For example,
[Dargonax's Signet] has a yellow socket with +10 str bonus. An inscribed topaz in this ring equals to 30 str and 20 crit, and a pure 40 str gems equals to just that, 40 str. This means that 20 crit has to beat out 10 str, which it does if crit's sep value is more than 10/20, or in other words, more than half. So, in this particular case, if your SEP value of crit is >0,5 than that of strength (which it often is in my experience) it's a dps increase to go for the socket bonus. My crit SEP value for example ranges around 0,6.
Be advised however that the differencies when you're gemming is often close to being negligible. For example, let's assume the Dargonaxx Signet above instead had a +10 crit socket bonus and my crit SEP value is 0,6. Then 30 crit has to beat out 20 strength, which means the SEP value of crit has to be higher than two thirds (20/30) of strength (sep value of crit >0,6666..). Since I assume I'm at an sep value of 0,6 crit in this example, the 30 crit pans out at 0,6*30= 18 strength, and as such the difference is merely 2 strength.
As a closing word, if you're not that interested in min-maxing your character (or if you can't calculate your sep values), you could always get 40 str in all slots where the socket bonus only is +10 stat, since that is always going to be a very good dps gain, even if it isn't always the ultimate choice.