They're all much of a muchness, railcards are usualy better than cash, even if only used occasionaly.
Despite what they tell you there are very few checks made on whether you have more than one account, but best avoid having 2 with the same bank (Hallifax and BOS etc). Just transfer in the £1500 loan per term from one bank to another to make sure they all get used. If yoru crap with money like my housemate then setup a DD from one account to the other with living allowance every week/month, and DD the rent from it as well. Then hide that card and just use the other account so you only need to budget weekly/monthly.
You'd be better off comparing the graduate accounts they transfer to after you graduate, all depends on how quickly they want you to pay back your overdraft or if you intend to even have one.
I just went with HSBC and got a 5 year railcard, but that was nearly 6 years ago now.