Downtown Moncton is the walkable centre, bilingual on the street in a way that is ordinary rather than performed for visitors. English and French both work, and you will hear both. The Magnetic Hill area, on the northwest edge, is a different geography: a commercial and attraction zone you reach by car, not a downtown block with a nickname. Dieppe sits against Moncton's side and holds a lot of the everyday city, including the airport side of the urban area. Treat them as neighbours, not as one hotel district.
The Petitcodiac tidal bore is a wall of water that comes up the river on the tide. People watch it from designated points. It is a natural event with a timetable you should check, not a hotel amenity and not a neighbourhood. Staying downtown makes a viewing easier to combine with a walk. Staying at Magnetic Hill makes it a drive. Neither stay includes a ticket, because the river is not a venue this guide sells.
YQM, Greater Moncton Roméo LeBlanc International, is on the Dieppe side, a short drive from downtown rather than a long airport haul. An early flight may still want a Dieppe or airport-side bed. A city visit wants downtown. Fredericton, the provincial capital, is smaller and quieter, a different night down the river valley, not a Moncton neighbourhood. If you want that quieter capital, use its guide. If you want the hub, stay here.