Single or double electric pump?

I can't decide whether a double pump is going to be worth it for me and would like any advice opinions.

I am returning to work full time, 3x12 hour shofts per week. My son is currently on a small amount of solids but mainly breastfed. When he feeds it has only been from one breast per feed, he never needs both. I wonder whether I should be using a double or single breastpump? For the days I am off work and inbetween shifts I will be breastfeeding again so the EBM is only for when I am work. I am wondering if I pump too much during my work days I am going to create oversupply issues on my days off?

I am looking at Medela Swing as single or Ameda Purely Yours or Medela Freestyle for double.

Many thanks.