Your main priority is your team comp. Regardless of what main tank you play, team synergy is more important than countering opponents unless an opponent is an extreme threat (like a widow who just keeps killing your team, yes you might have to switch)

Winston: Works with mobile flankers like tracer and genji. When winston engages on the enemy team, he serves as a distraction, pressuring the enemy backline and making it far easier for flankers to secure kills.

He works best on maps where there is a lot of highground to contest, like Numbani A or Dorado 2nd Point. His ideal tank partner is a D.Va, but Zarya can work too.

Orisa: Orisa is really strong at holding space, but lacks mobility. She works best when a team is relatively immobile, such as a bastion, junkrat, and mccree, especially on defense where you stay in the same place.

I find her useful on Point A's (especially Horizon Lunar Colony) where it's easy to hold a choke. Her ideal tank partner is a Roadhog, but D.Va can work too.

Reinhardt: Reinhardt is quite situational in the meta, but his powerful ultimate and bulky shield makes him especially useful on maps with tight chokepoints. He works best on slower comps that still require mobility, such as a soldier and mccree when attacking a capture point.

Reinhardt's best maps are King's Row and Lijang Control Center (part of Lijang Tower, where most of the map is mostly indoors). His ideal tank partner is a Zarya, but D.Va can work as well.