Its good advice from the dealer, tire profiles and radius vary between manufacturers even for the same supposed sizes. If you are not sure what to use then use stock tires, Pirellis are excellent so just choose the level of grip you are after for the conditions and your riding style. If you are predominantly commuting, its does not matter what you use, Michelin Road 5's are perfectly adequate, however if you are heading into the mountains every weekend and exploring edge grip, get Supercorsa's. The actual size 180/60 compared to 190/55, you will need to put a profile gauge on an inflated tire to compare along with an accurate radius measurement.
