I must admited that I have quited this game after the chaos of new aircraft market. (Frustrated by the existence of aircraft traders engulfing my market).
So, now is it still better to lease a plane than buying a plane? To me this is the most ridiculious and unrealistic thing in the game and seeing companies with a fleet of leased planes.
Leasing is the best option by far. You may think it’s unrealistic, but actually - there are lots of IRL companies, living large on a leased fleet. (At least one of my friends have an IRL ambulance company, with 20 leased ambulances.)
You may like it or not, but that’s how it works. And since everyone has the ability to lease, it’s fair play. 
It really depends on your business-concept. Just look in real-aviation: many airlines lease planes while some other airlines purchase aircraft or are doing a mix. My main airline currently owns only 46 of the 270 airplanes and my aim is to purchase them step by step.
if you have own planes, you can fly with 50% full plane and cover expenses, if you have full plane then you make fortune - its facts
but
when you start you don’t have money for buy even one new aircraft, so you can lease or take on credit
if you buy old planes - you will have hard jobs to fight with competition + high fuel consumption and maintenance cost will give you heading
but if you have money buy plane, not lease
you can use own plane for next 15-20 years and then sell it -
and question is: Do you want play this game next 15 years?
if you have intention for few month then lease, advance if faster, if you think to play long term, then buy
You may find this thread interesting. I did some rough evaluations on when it makes sense to buy aircraft on loans rather then leasing them - exemplary for a 737-900ER BGW, feel free to replace data with your desired purchase.
In general, loan purchase rarely ever makes sense due to sky high interest rates.
If you buy, do so only cash.