Just wondering what the advantages/disadvantages would be for each case. I work in a restaurant and can get 100's of seeds like tomatoes, pepper, eggplant, etc.. for free every day. I want to plant some at home to start my vegetable garden, will they work ok? Or will pre-packaged seeds grow better due to some coating or treatments?

As I am understanding your question, you are asking if you should take seeds from fresh food versus packaged seeds. Packaged seeds will be what they represent. The problem with taking seeds from fresh food, especially in a restaurant setting, is that you have no idea what you will get as the produce is likely hybrid varieties.

That all changes if you are saving seeds from fresh heirloom vegetables as they come back true (unless, of course, they have been crossed during pollination). This is one of multiple reasons that people grow heirlooms.

Remember that what you purchase in stores (used in most restaurants) is what has been "bred" to be good travelers for market and likely treated with various pesticides/fertilizers/etc. and not necessarily for flavor. Visit a friend's garden and get a tomato from them fresh off the vine and then get one from the grocery store - then you will understand.

Seeds from fresh heirloom veggies are fine; they should grow back true (barring cross pollination). Packaged seeds give you what you think you are getting. Seeds from store produce - a guessing game.