Pros
Culture. The CEO and CFO are geniuely nice guys who want and expect the best from themselves, their employees, and customers. They hired me with no experience and paired me with a brilliant senior engineer who taught me as much as he could at every opportunity. The learning opportunities are endless and I learned in a year more than internal IT would learn in 3. I really cannot say enough for how much they have done for me.
Kontras
Work life balance at MSPs is generally horrendous. They do their best to make sure you're not overworked, but sometimes a clients network goes down at 5pm and it is our job to get it back online. There isn't really anyway around this just a fact of life when working for a MSP. They always made sure that on-call duties were split evenly.