By simply looking at the name one can infer that 5-APB can with certainly to be structurally similar and more than likely produce effects similar to that of 6-APB, structural relatives have been noted as having many of the same stimulant/empathenogenic type characteristics as one another and are both considered to be agonist to the HT2A receptors. One of the few notable differences would be 5-APB lacking on the psychadelic feel that 6-APB holds. These structural relatives are also said to be quite potent, with a common dose falling around 100mg. Another prominent characteristic of both these benzofurans is the unforgiving nature if too much is taken. Some reports of this involve a user initially taking the right amount -100mg, and then for whatever reason administering another 100mg or so later In the night. This turns a fun and interesting experiment into an uncomfortable over agitation that can last for hours.
Although no legislation to date has been placed specifically banning/scheduling 5-APB, it could still be considered a close enough analogue of MDA, which would allow for prosecution under the Analogue Act.