Hannibal chose to cross the Alps and invade Roman territory by land from the north, rather than cross the Mediterranean and invade by sea.
Hannibal chose to cross the Alps and invade Roman territory by land from the north, instead of crossing the Mediterranean and invading by sea.
Hannibal chose to cross the Alps and invade Roman territory by land from the north, rather than cross the Mediterranean and invade by sea.
Hannibal chose to cross the Alps and invade Roman territory by land from the north, instead of crossing the Mediterranean and invading by sea.
The strict parallelism of two full verbs, allowed by "rather than", is stylistically preferable to the full verb/gerund imperfect parallelism of the "instead of" structure. The structure "instead of" + [gerund phrase] would never be correct on the GMAT.