If you split £80,000 of partnership profit equally between you and your wife, the first £10,000 for each of you would be tax free and you would each pay tax at 20% on £30,000 (£6,000.00) plus Class 4 NIC of £2,883.96 (£40,000 - £7,956 x 9%) and Class 2 NIC of £143.00 (£2.75 x 52), a total of £9,026.96. The total tax and NIC liability between the two of you would be £18,053.92.
If you made an £80,000 profit as a limited company, you would pay corporation tax at 20% which equates to £16,000.
Salaries above a certain level are subject to income tax and employee NIC at 12% and employer NIC at 13.8%, though there is a £2,000 annual discount off the employer NIC liability at the moment. Salary and salary costs (employer NIC) are deductible expenses so they reduce the company's corporation tax liability. Take a look here for the rates and thresholds for tax and NIC.
If you paid out dividends to the shareholders, whilst these are not deductible expenses for corporation tax purposes, they are not liable to NIC. Dividends are treated as basic rate tax paid as they are paid out of net of corporation tax profits so, if you have no other personal income than dividends, you would be able to withdraw £37,678.50 without incurring a personal tax liability.
Dividends carry a notional 10% tax credit so £37,678.50 grosses up to £41,865. That figure is the sum of the personal allowance for 2014/15 of £10,000 and the 20% tax band of £31,865. Dividends pad out above that level would subject to tax at 32.5% less the 10% notional tax credit. Take a look here for information on dividends and tax.
If you paid out £64,000 in dividends to two equal shareholders (£32,000 each) which would keep each of them within the basic rate tax threshold assuming they had no other personal income, the only tax liability would be the corporation tax liability of £16,000.
I hope this helps but let me know if you have any further questions.