I use both Photomatix (HDRSoft) and HDR Efex Pro 2 (Nik Software) as plugins from Aperture. Both applications can do a good job of merging bracketed exposures. Both offer considerable control over the resulting merged image from subtle to ghastly.
One point worth considering is that the plug-in version of Photomatix does not include the ghosting tool to manage movemetn across your bracketed images. The standalone program does but requires export of images from Aperture (& then re-importing).
Trial versions are available from each developer, so it would be worth testing them out to see which best suits your workflow.
I've found that the more I use HDR Efex Pro 2 the more I like it and the less I use Photomatix. Partly as a result of my love of Nik's u-point (no masking) technology. But your mileage may vary.