I'd go for the older pup everytime.. having had 2 pup's from 8 weeks old and a 2.5 yr old rescue... give me an older dog with issues anyday over a puppy
You may have problems with them being bitches so close in age.. but they may be fine, it's impossible to know at this stage.
In terms of work and expense, yes 2 dogs are pretty much double that of one and for me the biggest downside is that I don't feel as close to my two individually as I did when I had just one. I get round this by giving them lots of individual attention - they are walked separately most days and trained separately too. I love walking them together and it's a lot of fun, but they do tend to hunt more and egg each other on and if they're going to be a little deaf, they do it when they're together - if I didn't have young children this wouldn't be so much of an issue but it's a pain in the bum trying to keep track of all of them on walks sometimes
. I think I've agreed with myself that in the future it's likely I'm going to stick with one dog that's a bit of a handful - I like the challenge and the bond you can have with a more highly strung dog (which is why I got two dogs as my second cocker pup was very different to my first and was a bit too easy if you see what I mean!) Having said that, I couldn't pick between my two now, they both offer very different things and they're just both a massive part of our family
If you absolutely love everything you have with your current dog, then think carefully about adding to this.. as it will change the relationship you have. If you feel you're missing something and need more of a challenge then that's a good indication that you should get another
Good luck with whatever you decide!