Google uses titles as an important step in determining whether a website answers "searchers intent" - should google display that page on the SERP.
The composition of a title is far more complex than the obvious. The title has a strong SEO focus but also it has to be optimised for clickability. So there are trade-offs. An example is we have changed titles - a few words around and seen a 6 times uplift in CTR. So optimising for the customer is integral.
So the first thing to do is determine keywords - then trade off with click ability. I am not sure I would start with the word buy. A standard method is
Most Important keyword | Second most important Keyword | Brand.
Should be a nexus between the two keywords. Also the title can only be 512 pixels long before it truncates. Hence the title has limited space and two competing components clickability & SEO. Big decisions.
To answer your question, from the information at hand on the and v &. It is semantics but i agree with Linda the latter is more attractive and secondly it uses less pixels.
Let me know if need any more information.