If it has been teched out and he gives you a warranty it is an excellent deal. Yes they both do straight and zigzag. The 503 can not to the reverse stitches used in stretch stitches. The Kenmore may or may not do a few decorative stitches. Both are capable of doing hemming - the 503 would have to have the hemming disk. The Kenmore has it built in. Actually the two machines would be good companion machines because the Kenmore does more utility type stitches and the 503 is capable of doing nice decorative stitches.