According to the SOC, you need the dual recommendation letters whether you have SRS or just an orchi - any genital surgery, basically.
As to pros and cons, many different arguments, but I think it's a decision you have to make yourself. I'm opting for one despite the danger of shrinkage and stuff for a few reasons:
1) Finances - SRS is not in my foreseeable future, and I need to take some kind of concrete step in the meantime. Also, a loophole here in South Africa allows me, in theory to legally change my gender marker on an orchi alone, so that is a huge plus.
2) I don't want to be on Anti-Androgens forever. Besides the additional costs, they are dangerous in and of themselves long-term.
3) Hormone balance. I've heard many people say that, after they've had their testes removed, whether in SRS or an orchi, they find their feminisation speeds up lots as the Estrogen is no longer being opposed by the T naturally in your system.
So yeah, those are the factors that finally swayed me. Listen to the arguments for and against and decide what are priorities for you.
Good luck sweetie.
Mina.