The gain made from the disposal of a capital asset would normally be subject to capital gains tax (CGT) at lower rates than the gain made from the disposal of trading stock, which would be subject to income tax.
R300 000 per annum is not exactly a massive turnover nowadays. In fact, it's a mere R25 000 per month - similar to what a fairly junior manager in a corporate earns nowadays, before one takes costs into account.
SARS has recently published draft legislation regarding the imposition of an environmental levy on electricity. Due to come into effect from 1 October 2008, it will be imposed on electricity generated in South Africa at a rate of 2c per kW/h.
The tax that you pay on the two options are markedly different. In the case of the company car, you are liable for fringe benefits tax based on 2.5% of the so-called "determined value" of the vehicle (normally calculated as the cost price excluding VAT and finance charges).