Sunderland have a bigger ground and a massive budget.
Sunderland have a bigger ground than Spurs, but that won't be the case once White Hart Lane is redeveloped; however, even now I'm sure their income is far higher than Sunderland's: the 36,000 at Spurs will be paying a lot more than 40,000 at Sunderland. Sunderland is a poor place and the disposable income of the average supporter is very low. Sunderland's budget since Niall Quinn became Chairman has been bigger, in real terms, than at any time since the sixties. It remains lower than Tottenham's though, and the gap between the two clubs' budgets can surely only grow bigger, particularly when there are 58,000 at every Spurs home match in a few years time.