If you like your Vibe you should like the SDX as well. They both can be set up to be very stable, agressively quick or somewhere in between. The SDX weighs less by about 1/3 lbs (150 g). IMO, with a 50 engine the SDX outperforms the Vibe for this reason . The Vibe is beefier all around, so it may be a great choice for one of the new larger engines like the NovaRossi57, OS55 or YS56. IMO, the Vibe needs the extra power and the airframe should handle it, I hope.I already bought the NR57 and will likely put it in my Vibe, I'll get the OS55 for my Raptor (it fits) and either the NR57 or OS55 for my SDX. My goal is to keep the power to weight about the same in each model.You won't go wrong buying the SDX unless you want something that doesn't fly anything like your Vibe, a T-Rex for example.