I am happy with 355, but some other people are happy with 406. People are different... I toured 770 km with medium/heavy luggage (big rear racktop bag, two small front panniers, front handlebar bag, staying in hotels). Picture at https://www.flickr.com/photos/gunnst...7710551162926/
Maybe try the first Birdy tour with the wheels you have, and then if you're not happy then you can switch to 406 before your next tour?