dic = {'bsx_8612': [23, 567, 632], 'asd_6375': [654, 12, 962], 'asd_2498': [56, 12, 574], 'bsx_9344': [96, 1022, 324]}

print max(dic.items(), key = lambda (k, v): sum(v))[0]

# Python 3
print max(dic.items(), key = lambda t: sum(t[1]))[0]