They are both past tense and have similar meanings. The expression "used to work at the company" emphasizes the fact that something changed and I do NOT work there now. The form "used to do" (expression) generally gives us more information than "I did" (past simple). For example: I smoked. (Yesterday? For 20 years? Once? In the past? It could mean any of those!) I used to smoke. (means I smoked regularly, but I quit smoking and now I do not smoke anymore.)

Hi your 1st sentense is "simple past" we use it when something has happened in the past and it's already finished. I used to do something = I did something regularly in the past but no longer do it. the difference is that: the 1st one has happened regularly but the 2nd one hadn't been repeated. Note: Do not confuse "I am used to doing" and "I used to do". 1.I am used to ( doing) something = It isn't strange or new for me. 2.I used to do something = I did something regularly in the past but no longer do it.

هذا زمن ليس موجود عندنا في اللغة العربية وهو يدل على الاستمرارية..: used to :يدل على الاستمرارية في الفعل أي أن الفعل أخذ زماناً معيناً لتحقيقه أو أن الفاعل اعتاد على أن يقوم بهذا الفعل.

We use 'used to' for something that happened regularly in the past but no longer happens.