Safari in Tanzania: different estimates of 1.800 euros, what am I comparing badly?

For six days of safari and four in Zanzibar I received three very distant proposals. All say “full board”, but change parks, number of people on the jeep, internal flights and categories of lodges. I can’t understand what differences really affect experience and what are just business names. I would like to compare quotes on homogeneous items before choosing, also checking insurance, tips and cancellation policies. I am interested in a comparison based on recent experiences: indicated travel period, what really wo…