UE4 on Late 2009 imac

Hey everyone,i have ue4 installed on my late 2009 iMac with 8 gig ram and on my late 2011 13 inch with 4 gig ram.both on 10.9.4 .I don’t know why but the game engine literally LITERALLY runs smoother without lag or crashing with the macbook.only thing is that the fan runs very hard. On the iMac its a tad bit laggy and nowhere near as smooth any idea why?Reading the system requirements you would think the iMac would be better but Iam seeing otherwise.Iam considering buying a new iMac but don’t know which one would be best to go with.I just thought i would share my experience with these two machines with everyone.

The late 2009 iMac has an ATi 4xx0 series GPU which only supports OpenGL 3.3, whereas UE4 performs best on later OpenGL 4.1 GPUs. As a result if the GPU in your has an AMD 6xx0/Nvidia 6xx/Intel HD 4000 card or newer then I would expect UE4 would perform better on the Macbook than the iMac.

what version do you have installed on your imac? when i try to use 4.26 it just closes the launcher but doesnt boot UE.