My limited knowledge
As a company
1.You can carry forward losses into next financial year unlike a sole proprietorship
2.You liability in the company is limited unlike in the sole proprietorship where you personally assets can be attached incase of a liability
3.You stand a high chance of avoiding taxes when you register a company than with a sole proprietorship, E.g You can register you house, car etc in the business name which will allow you to deduct WTA before taxation.
4.Witha company, you can expense management expenses and fees unlike a sole proprietorship e.g salaries, rent,transportation etc.

The main advantage of a company over a sole proprietorship is the reduced taxation

True @swenani. Not only do you get to claim Wear and Tear on your assets but also your asset maintenance expenses e.g. Motor vehicle fuel, repairs, insurance, house repairs etc are deductible for taxation purposes

KRA will however expect you to compute tax from the salary you pay yourself for the benefit of a company car(if it doubles as your personal car) and housing benefit for the house you live in

Assuming that you mean a LIMITED company, tax will be a flat 30% of profit.

If proprietorship, tax will be according to normal individual tax brackets - same as PAYE brackets

If you have several businesses,you will pay less tax if you register some businesses under your wife's name rather than registering everything under your name.

If your wife already has other sources of income exceeding Kshs 466 P.a the only difference will be the monthly tax relief of Kshs 1,162 since the two of you will be claiming separately.If she has no other source of income,the tax difference will be marginally savings made due to the savings made on the graduated tax rates on your income in excess of 466k