Best heli?
Do it in the one that is closest and most reliable/available to suit flying at least 2.5 times a week… especially at PPL level were getting basics down is most important. R44 if given the choice as there are alot around and you can bring your mates easier than a 2 seater. (Raven II with injection is best compromise as death by carb ice isnt a great idea..)
Flight schools have failed since the dawn of time so never pay more upfront than you can afford to lose, go modular so you have options to swap schools when something happens.
Also, please consider getting a set of flight sim controls and VR goggles… saves a crapload of dosh when learning to hover (in my case, Puma Trainer Helicontrols, Xplane 11 R44 and Quest2 VR goggles)