Some super-trainers may look almost identical to super-shoes, but there is always some aspect of them that differs from the racing shoe in a brand’s line-up. This could be a different material for the plate, or a different foam in the midsole, or a more padded upper and thicker outsole, which adds weight you don’t want in a super-shoe for racing but is worth having to add comfort and grip in a trainer.
Sometimes the difference can be even more subtle, like a slightly different version of the same foam and different geometry that makes the super-trainer more stable and less speed-focused than the racing shoe. For example, the New Balance SC Trainer v2 looks very similar to the New Balance SC Elite v3 racing shoe, but the difference in how the shoes feel on the run is very noticeable.
The main differences can be summed up as super-trainers are usually a little more comfortable, stable and durable than super-shoes, which are purpose-built for race day. Super-trainers are also generally cheaper.