Katydid or Cricket?
I think photos will be the most helpful large-scale identification aid. In general, katydids’ back legs are quite long and are close to their two pairs of front legs. Their wings meet at the top in a somewhat tent-like appearance. Combined with their generally larger size, they stand higher than crickets. Crickets’ wings lie on top of each other and their rear legs are not quite as long. They appear more horizontal. When I photograph katydids, I typically take picture from the side to get more of the insect and its characteristics. For crickets, however, I often photograph from above unless a male tree cricket has his wings raised at a 90 degree angle to sing.
Here are photos (Clockwinse from the upper left) of Black-legged Meadow Katydid (a small species) and a Greater Angle-wing (a large species) from the side followed by a Texas Bush Katydid taken directly above and then from side.
Now, here's a Two-spotted Tree Cricket, a Black-horned Tree Cricket. a Fall Field Cricket, and a Jumping Bush Cricket. The names are listed clockwise from the top left, and and all photographed from above.
Also, the cerci at the end of the abdomen are much more prominent on crickets – especially ground and field crickets. (Females have both cerci and an ovipositor.) Tree crickets' slender cerci are not as visible because of their wings.
Female Striped Ground Cricket
Male Fall Field Cricket
The visual comparison information is interesting and important. Even more important is how to listen to the songs. Cricket and katydid songs are quite different, and you can read and listen to two of my Listening in Nature posts that discuss and demonstrate how to listen to both crickets and katydids. These are tutorials that will be very helpful in the field or in your backyard. You can find them here:
Cricket Songs: General Characteristics of Pitch and Rhythm