Pros
If you're coming on-board as an unskilled worker with a High School Education or equivalent then the opportunities to earn a decent wage with amazing benefits is definitely there at UPS-Supply Chain Logistics. UPS is renowned for its benefits packages which I can testify as being the case during my time there. You'll have the opportunities for on-job training to work in any specific area within the warehouse, be it shipping/ receiving, quality assurance, inventory, or order picking. If you're coming in with a degree and perhaps some previous management experience it is UPS's policy to start you in at the bottom. I did have a friend of mine reach supervisory level within a matter of 5-6 months however and he was coming in with a degree and some years experience in management. UPS-Supply Side is non-unionized which could be a pro or con depending on how you look at it, personally I found it beneficial as I was able to work a great deal of overtime (paid at time and a half) which helped me later pay for my year of tuition in college.
Cons
It's a warehouse environment and as such there is little human interaction in many of the tasks that you'll perform, this can be bad and good. It is also particularly isolating depending on the shift/ hours you take. Tasks can become rather repetitive but that is the nature of the work. During my time there I sought out training in all roles that took place in the facility and worked in those roles for some time, that helped to alleviate some of the stagnation that can occur when working in a warehouse. There is also a point of diminishing returns in terms of showing initiative, you will only be rewarded to a small degree for harder work ethic assuming you aren't intent on pursuing a management role. They will capitalize on any extra efforts you give without much or any benefit to you.