Making Rose boutonniere is probably the easiest out of all other flower boutonnieres... Why? There are couple reasons. First, the stem is hard and strong comparing to other flowers. Second, the flower bud is durable and hard to crush. Third, when the rose opens (if it does opens... sometimes it doesn't open at all), it opens up to a big bloom. Other reasons such as it's easy to wire and tape without being worried about killing it by pressing too hard. And it won't have a sad look too easily if its out of water for a while. And it's available and affordable.
Cymbidium orchid is the best flower to make boutonniere since it will last for a long time without water. However, it's really take a long time to make it into a boutonniere, plus the price for cymbids are not cheap. And oftentimes the flower will turn brown easily if petal get damaged... (cannot peal it off like rose...)
Dendrobium orchids are good choice of boutonniere making. But they are also very delicate and take time to wire carefully. But they also last long too.
I got many customer want stargazer or Casablanca lilies for boutonniere or corsage... It usually gave me headache when I heard it... They are just too fragile to wear as boutonniere or corsage... The 5 petals may only have 1 petal left at the end of the party if you are lucky... I ususally ask them to change their mind...
Gerbera daisies are beautiful to make corsage or boutonniere. But using a water tube to hold the moisture may be a good idea if it's going to be hot at the party. Alternative way will be wiring the Gerbera Daisy stem with wet cotton sealed with foil or cello. Because once the Gerbera daisy is dehydrated, it will give you a very sad look...
Carnation and daisy are OK too. They are very affordable in terms of the price; but with the same amount of labour like making rose boutonniere, florist would rather sell the rose boutonniere than a carnation one. But for DIY lovers or junior florists who need lots of practice, these flowers are great because they are very economic.
By the way, I forgot to mention Calla Lily... It's a great choice for boutonniere but not so good for corsage... Anyway, it will be next time's topic =)