ODE's big matrix solver (the default in gamestudio) is a lot slower than newton 1.5. ODE's iterative solver is faster than newton 1.5 but very unstable.
newton 2.0 should be faster than both ODE solvers yet still be very robust.
newton also is the easiest 3rd party physics engine to use with gamestudio because it uses a c-api instead of a c++ one and thanks to the work of people like vet.