IMO, it depends on what you need the pliers for. I usually use my pliers to hold a small nut while tightening a bolt from the other side, hold onto and/or bend small metal things (like a key-ring, small bar spring, or the edge of sheet metal), or to get leverage on something I can only fit a finger or two on (like lifting a small drainage grate). If you use the saw a lot, the SAK's saws are better than their same-size equivalent Leatherman counterparts. Depending on your usage of the pliers, you might be able to get away with a Leatherman Squirt PS4 on your key-chain, and keep the SAK in your pocket.
Also, be aware that as you add more stuff, weight becomes more and more of an issue. I prefer my Juice S2 to my CS4 when I don't need a saw, awl, or corkscrew because of the weight. If I don't need pliers but still need a saw, I like my SAK Fieldmaster better than my CS4 because of the weight savings and much easier saw action on the SAK. The Leatherman's saws cut only on the pull stroke versus SAK's cutting in both directions... yes, it's noticeable if you use them a lot.