The only way to compare across options is to come up with your own, personal subjective value of what each point is worth. And, in my view, the only way to decide what a point is worth, is to ask a simple question: What is the dollar value at which I would be ambivalent between being given cash and being given the point?

So, using that formula, here are some values you might assign. (I'm just throwing these out there):

SPG: 2.2 cents
Amex MR: 1.6 cents
Chase UR: 1.9 cents
Hilton: .5 cents
British Airways: 1.25 cents

These values do not always remain static -- sometimes you may be very low on a certain currency and want to build it back up. Let's say you're shooting for a redemption on SQ, and the only way to get it is with SQ miles, so you want Amex and so your value goes up. But, in general, let's just stick with those numbers so the process make sense.

These values help for two things: (1) how should I accumulate, and (2) how should I spend?

Let's say you have a purchase to make for $1,000. It can be manufactured spend, or a real purchase, etc. Let's say you have a variety of different cards to make the spend. Which should you use? Just apply your values.

Let's say you can get 2x Amex on this purchase, plus be 1/30th of the way toward the spending cap of 30k, which nets you 15k extra miles (which you intend to hit). I would say that for this purchase, you will get 2,000 Amex, plus the .5 bonus, for a total of 2,500 Amex. (Put it another way, this is 1/30th of your spent toward the 15k. 1/30 x 15k = 500.) So, now, what value are you reaping if you use your Amex card on this purchase? 2500 x 1.6 cents per point = 4000 cents, or $40.

Is this the best option? With 2 percent cash back, you would have gotten $20 in value. Let's say the best you can do on any other card (SPG, for example) is 1x, so that you'd get 1,000 SPG points. Do the math? 1,000 SPG points x 2.2 cents per point = 2200 cents, or $22. Etc.

Now, use the same process for redeeming points. Suppose there's a British Airways flight you want for 25,000 points. You could use 25,000 amex, which is a cost to you of 25,000 x 1.25 cents -- or $375 in value. You could use 20,000 SPG, which transfers to 25,000 BA, so that's 20,000 x 2.2 cents -- or $440 in value. So, the Amex is better. Etc.

The key is that everything requires, at the outset, a rudimentary understanding of your personal, subjective value of your points.