Intimidation-

Effectively the same thing as Persuasion but slightly moreso and only for the angry option, there’s very little reason to take this perk mechanically.  It can be interesting for seeing all the possible results of some interactions, but otherwise you may as well just stick with Persuasion.

Investor-

If you sell a lot of loot (also known as being a pack rat in dungeons), then this perk can be hugely useful, particularly when stacked with Merchant to enable you to sell everything to the same merchant.  As with Merchant, it’ll cut down your busy time between quests a lot, and goes even further to ensure that you can actually sell everything, making it worthwhile for pretty much everybody.

Fence-

If you’re part of the Thieves’ Guild, you probably don’t care about this other than from a pure-convenience standpoint.  If, on the other hand, you prefer to operate as an independent, then you’re going to save yourself a lot of trouble by taking this perk.  Everyone else only cares because of what this leads to as the top end.

Master Trader-

Do you loot everything?  Do you frequently run merchants out of gold selling them things and want to get more gold off them to pour into another merchant or just into buying ALL THE HOUSES FOREVER?  Taking this perk will more than double the gold some merchants have available, giving you plenty of chances to get more money moving in the directions you move it in anyways.  Also useful for thieves who want merchants to have more coins they can steal.  As an alternative to selling stuff so you can buy ALL THE THINGS, just sell things to merchants until you have tens of thousands of gold, then dump them all in a big pile in the corner of your house and jump on it to watch the coins scatter.  It’s a lot of cleanup to do afterwards, but whee flying shiny things!