Sorry, I'll expand a bit:
I think Palermo will demand far more than £25m for their prized asset - they'll push for something obscene like £50m (well, the world's a twisted place). Adam will cost £10m max (otherwise **** off Hollaway) - he (Adam that is) is up to speed with the demands of the Premiership . Pastore age & potential-wise IS the more desireable option, but it's a question of:
A) Are FSG prepared to pay up for a player who has massive potential ?
B) Do they want an instant return on their investment ?
If the latter, then Adam is arguably the safest way to go - he wouldn't be my first choice, but in the end it all comes down to two things: owner ambition & available transfer funds - & the two aren't mutually exclusive.
I think FSG will designate around 50m for Kenny's 'war chest', the rest being made up by player outgoings - so work out the numbers for yourself.
PS: Viva Catalunya !
The £25m price tag I'm quoting is based on what YDaphus has been saying on Twitter, and he is a very reliable source, got our January transfers spot on, so if it was £25m for him, and we could get a left-back, centre-back and one or two wingers all of which could challenge our first team, and still have £25m to spend, I think it would be silly to spend it on Adam instead.
Also, to answer your A or B question, I honestly think FSG may choose option A. Just look at Andy Carroll, £35m for a player who has bags of potential. Of course he's great now as well, but just look at Pastore playing, he is fantastic too, and even younger than Carroll! So yes, I think Pastore would not only be able to offer something for the future, but next season too. He would be as important a player as Charlie Adam immediately, probably more important, but I do believe that he would be an FSG-type target.
YDaphus seems to be a great source, so I guess I'm treating his Twitter and Anfield Index posts as the Gospel