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.
Just to give you a counter point, I've used both the Nik and the HDRsoft programs and now pretty much only use Photomatix generally in its plug-in mode. Ghosting isn't an issue for me as I only do HDR off of tripod shots. (For a complex set of shots I will export and use the stand alone version. An extra step, but not really a problem.) Both programs work, but to my eye Photomatix creates a better image. You probably can't go wrong with either, though I - and many others - are concerned for the future of Nik since it has been sold to Goggle. As Mtb suggests, download both demos an play with them.