Delph would improve us because if he came he would know he won't get many starts will eat up a HG spot and that means we could sell Fernando to bring in a top quality foreign player.
He's also got plenty of experience to be brought on in certain situations to do a job.
If we brought in Ward-Prowse we would be basically buying potential but he wouldn't be starting enough to improve his ability. Therefore we would have to either sacrifice one of the big stars or loan him out thus defeating the object of improving the squad.
I can see us looking at him next summer but with a rumoured £150m to be spent £10m for a decent HG player is decent business. Providing of course he's not instead of any of the major signings