Big aperture zoom lens are too cumbersome to carry around and usually big aperture means more expensive. When there are more lens elements, more internal reflections will occur. With modern lens coating technology, that can be minimized but general rule is - try not to use it in back lighting situation. Most zoom lenses performs miserably in such situation despite all lens manufacturers claim it rival a prime lens. Over all, it is still justify to invest into a zoom lens in terms of total flexibility and mobility.
All brands are the same.
Your entry into photography needs you to decide a selection of a camera system which you can grow with. It primarily depends on how well the support your local distributor or how extensive their local network of a particular brand of camera is. Secondly, if you are serious with photography later, how extensive a particular camera system is, can be an important factor to be considered before you make the choice. That is to protect your investment in the hardware for future growth. Assuming if your prime interest is on macro photography, selecting a wrong system during entry stage could result in a fresh new investment because may be the brand that you have chosen doesn't support macro work at all, like there are no dedicated bellow or ring light to retain your auto exposure features etc.