Chainstitching is popular on jeans because it enhances the roping effect. Google image it and you'll see what it is. Its when the hem fades like a rope. Anyway, a regular lock stitch can achieve the same effect. The chainstitch works because of the way the machine pulls on the fabric or some such techno mumbo jambo. Basically, if you can get a lock stitch machine to do the same thing, you'll get the same result. And to add more food for thought, eventually the lock stitch will develop some roping, but to what extent depends upon more factors than I can handle. So, in answer to your question. For chinos, it doesn't matter IMO. Get whatever the manufacturer put on it if you can. Otherwise, decide whether or not you actually want to hunt down someone with a Union XXXXXX whatever machine just for a chain stitch.