So, it appears your agency choice will be based on repetitive rumours (probably the same bar session) from people that I suspect you really don't know that well and from what you've heard on this network? Excellent decision making module.
Throw this in the pot then, I've heard that a similar number would like to change to said agent but most of us are actually ambivalent about any of the agencies.
It also appears you've been misled into thinking that your choice of agent will be contract defining. It's not, although I agree it is probably difficult to change once in. If there were to be an 'ace' of an agency, wouldn't we all be signing up but we're not so that's the best evidence you'll ever get.
Once you've selected your agency (sounds posh doesn't it) and if you absolutely insist on your new adventure, then good luck with your sim and medical.
It'll be about two years before you get on line so I doubt I'll be around to take up your drink offer.