Oooh! deffo both hard but in different ways. Both CAN be difficult to reason with. Both have similarities in terms of parts of the brain/emotions/chemicals etc outgrowing others. Both swing from dependence/independence at lightning speed.
Toddlers are more portable, and with effort, muscles like Fatima Whitbread, and a will of steel, can be hoofed up to their bedrooms for a 'calm down' for a wee while.
Teenagers tend to be bigger than me, and like to argue with me like Jeremy Paxman on a grudge match. it's less physical and more emotional with teens - both require a degree of hostage negotiation techniques.
Having said that, Ds1 is 16, and we've had our ups and downs at times - he is quite lovely, and to see him growing up and developing his own opinions/values etc is great!
Nailbiting at times, as you gradually trust them with more and more stuff, and sometimes you have to rescue em...