Issues in the comparison of particle perturbations and numerical relativity for binary black hole mergers

Recent work on improved efficiency of calculations for extreme mass ratio inspirals has produced the useful byproduct of comparisons of inspirals of comparable mass by particle perturbation (PP) methods and by numerical relativty (NR). Here we point out: (1) In choosing the rescaling of the masses, consideration must be given to the differences in the PP and NR methods even in the earliest, least nonlinear regime; in particular barycenter effects must be addressed. (2) Care must be given to the comparison of the nonspinning remnant in PP and the rapidly spinning remnant in NR.