Check this out:
1) Linking out helps you if you link to relevant sites.
2) The reason that page rank decreases if you link out to partners that don't reciprocate is because of the iterative nature of Page Rank (it is a recursive function). So its not like you "lose" any page rank for linking out, but you don't gain any from the people you link out to as Google recalculates the page rank for the 2nd, 3rd, 4th times, etc. See page rank is not a one time calculation. It takes many iterations of the process. If you don't understand this, go to Google and search for Page Rank. Then READ about it so you understand it.
Lets say you have a homepage that links to two pages off your site with no internal links. Obviously the page rank is divided into 2 and distributed to the two sites that you link out to. But if one of those links is internal, then half the page rank goes back to your page and half to the external site. The half that comes back to you is then used for the next caluclation of page rank thereby increasing your total page rank at the end of all the calculation cycles. The effect is real as I have seen it happen where adding lots more internal links to my homepage increases my page rank because a great % of page rank is being passed back into my site.
3) Keep in mind that there are two competing qualities to Google's algo in play. Page Rank and the number of links you have to relevant sites. Where the happy medium is, only Google knows, but they often times have competing algo factors to make it too difficult to reverse engineer what they are doing. Currently, I wouldn't worry about hiding links except in the case of affiliate links which I believe are penalized in Burbon. As long as when you link out you do so from pages that have alot of internal links, the "page rank leak" I believe in most cases will be outweighed by the strength of linking to relevant content and the boost that it gives you. Of coarse this is just my opinion but sites I control have seen rankings increase by linking to relevant non competing sites.
Keep this in mind also, if you mask where a link goes, you get no credit for linking to it. So by extension, if most of your links are hidden from Google to "protect" your page rank, they will also give you no credit. And with page rank being somewhat topic sensitive nowadays in terms of what is really ranking websites, the PR that you save is probably not worth the trouble and may actually hurt you.
All this is my opinion. Proceed at your own risk.