Regardless of feature differences (e.g. pockets, zipper length etc), I would make the assumption that triathlon specific clothing / fabric choices would be tested and developed with swimming in mind. Depending on the company, this assumption may not hold.

The materials that we use in tri-suits are different than our cycling apparel as they better maintain their form when wet.

With that said, it will be less of an issue if you are swimming in a swim-skin or wetsuit.

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Fit differences will be huge.

An aero cycling jersey is designed to be tight when bent over riding so there are minimal creases and wrinkles. If you stand up straight in one it will feel a little constricting in the chest area and may not be your cup of tea if you are going to run or swim. However if you unzip it's generally a non-issue. The aero jerseys i find are also a little less durable than other products. They are meant for race day use mainly and if you use them on a daily basis the constant washing and thin, tight fabrics will wear them out quick

The tri jerseys are designed with the fact that you are going to run in mind so will tend to be abit looser.