Well pro league plays Bomb only, so fireplace is the bomb equivalent of train room on kafe. It depends on whether you're playing bomb, hostage, or secure area. I'll assume secure area for now.
Bank: lockers, open area (though archive is a good second choice as well)
Border: armory lockers, offices
Chalet: snowmobile garage, dining room
Club House: arsenal room, bedroom (personally I find bedroom to be a bad place to defend. however club house is getting overhauled in the next patch in a couple weeks so this map is going to change significantly)
Coastline: penthouse, billiards
Consulate: archives, garage
Kafe: train room, cigar (i like cigar second, a lot of people prefer kitchen)
Oregon: laundry, bedroom
Skyscraper: tea room, office
Theme Park: drug lab, daycare
Tower: fuck tower
These are the general first options, my second picks are usual choices but second picks vary from team to team and map to map, some second picks are stronger than others whereas some second picks are barely better than the third so personal playstyles and choices come into play.