I have had both the Cricket and the SLB for many years. I like both a lot, but as good as it is, the Cricket feels almost flimsy compared to the SLB. Do not take that as a slam of the Spyderco, it's just that the SLB feels like it would stand up to more heavy duty use by far.
If you are just looking for a knife to open letters, cut string, etc., either one would be a no-brainer. However, for tackling the slightly more heavy duty tasks that pop up when you do not have a larger knife (and since both of these are quite small, almost anything other than a SAK Classic is going to be bigger), the Al Mar is ideal. One of my all time favorite knives.