Pros
Actually has vacation time, personal/sick time for employees after 1 year. Has a union that gives employees access to a clinic for free right away. Most contract security companies offer none of these benefits at all, ever. Some good, long-term clients and a few very well paying sites if you get lucky and can get in on them.
Kontras
It's a contract security job. You have little job security depending on the site you work at, the hours generally are bad, you will be asked often to stay late or to cover someone else's shift or come in early if someone else calls out usually with little or no notice. Clients can remove you from their sites for no reason at all if they like. Many sites have pay rates that make the job a "second job only" but they want you to work like it's your first and only job and give 100%. There's some nepotism here, it's a family company and friends of the family too, but nothing major.