Until and unless Social Security is dramatically reformed, we are better to pay the extra 2 percentage points. If the government had any sense, they wouldn't have cut payroll taxes in the first place.
All this tax cut did was to put Social Security in an even more precarious position. It was touted as a way to spur economic growth but it couldn't and didn't.
Only cuts to capital gains taxes and income tax marginal rates can spur the economy.
Your points are well taken. Unfortunately, with the weak economy, any decreases in disposable income will hurt the economy by reducing consumption. And, the political reality is that there is no SS trust fund and there is no trust that our government would use the new taxes to improve the precarious position of SS. The money will be squandered as it usually is.