Which ticker code to buy when the company has two different tickers? (e.g., VACQ & VACQU)

So I saw Vector Acquisition in the news recently. I was investigating if they would be worth investing in.

However I found it was listed under two different tickers VACQ & VACQU. They seem to be listed on the same exchange and are not (as far as I can tell) like BRK.A and BRK.B e.g., different sized share slices and or different voting rights.

In the case of VACQ & VACQU they both have a similar price but not exactly (give or take a few cents).

The only difference I could find was one was called Vector Acquisition and the other Vector Acquisition Unit

I have also seen this with other companies like LVMH.

So lets say I do decide to buy some shares in say Vector Acquisition (or whatever).

How do I work out the difference between the different tickers and decide which of the two (or more), is the best one for me to buy?