2" shower p-trap with our without union?

I'm installing a shower on my main floor and am wondering if I should use a p-trap with our without a union. The trap is accessible from below from the basement. From what I've read, it's not recommended to use the one with union. Thanks for your help.

A 2" trap is easy to snake through, so I can't think of many reasons I would ever want to take it apart and put it back together. It would be another place to leak though.

If it is a long run across the basement, you might consider adding a wye in the line for a cleanout.

If you are looking for one more problem, then go for the union.
Most codes want solvent fittings that are hidden because unions are always a problem later on.