I have flown with many airlines on this route and I still enjoy Turkish Airlines the best. Their friendly, cheerful, helpful staff are a credit to them. The seats on this route are larger than on other airlines on the same route, the in flight entertainment is varied and generally up to date. The food is some of the best I have tasted on my various flights. No airline food is going to be perfect because of the nature of the challenges but Turkish Airlines do a good job. On the route I take between LHR and Dar es Salaam there is a short stop over at Istanbul. Sometimes very short, like less than one hour from landing to taking off again. In these instances the ground crew are totally organised and usher you through smoothly and without fuss. What I especially admire about these short stop overs is that my hold baggage has also always made the transition equally smoothly and arrived on the same flight as me at my destination.
The final and possibly the most important to some, including me, is the price... They can offer all this at excellent prices without compromising on their quality.
In summing up I would have no qualms in recommending Turkish Airways and will fly with them whenever the opportunity arises.