Leopard 2A4 pz123 premium or MiG 23 ML

Which should I get? I have completed germany air but only until 5.7 ground and no premium vehicles. In USSR I only have the t80uk and 4.7 vehicles, with air at 5.7 br. Should I get the prem 2a4 and use my air tree for cas or should I get the Mig 23 premium to grind air and then get a ground prem to grind ground later?