Sample sets are usually offered in several variants: Wet, Surround and Dry. The majority of people should opt for the wet or surround variant of the sample set where the church reverberation is included in the samples. The church organ usually sounds convincing only if immersed in the reverberation of the church building. A dry sample set - samples recorded close-up without any reverberation - is ment for very special purposes, it is not a virtual instrument which can be played "out of the box". The dry sound of single pipes is usually not pleasant. Just imagine sitting inside the organ case and listening to the organ music from there - you will be disappointed. Hence, it is probable that the dry sound of the dry sample set will sound very disappointing if used out of the box. Special treatment must be done to the audio to get the sound you want (but this is the advantage - you shape the instrument exactly to your liking, what is not possible with the surround variant).
I have already had users who bought the dry sample set (because it is much cheaper and because it needs less powerful computer and less RAM) and then they told me openly they were disappointed. For this reason, there is the special "crossgrade" option from the dry to the surround - if you are not happy with the dry, you can get the surround instead for a special price so that you are happy again. But I say clearly, dry sample set is usually disappointing if the user is not able to treat it properly and build his own instrument out of it.
I always say that the dry set is as giving raw pipes to an organbuilder: you must construct your own organ out of this material, you must voice it to suit your needs, you must place it into an acoustic environment (into a real church, or using some reverberation effects), furthermore you must position the divisions to the places where you want them via many and many audio channels ... it is a lot of work left to you. The result is rewarding: it is often behaving as well as real pipes in the given acoustic space so the sound of the organ can hardly be distinguished from a real organ installed in that place. However, it will be a new instrument, it will not sound as the original instrument in its original acoustics. It will sound as if the original instrument is tranferred from there to your environment and revoiced for it.
So, acquiring dry sample set means mostly problems for the "average" Hauptwerk user. The dry sample sets are mostly used by specialized companies who use them for their installations: church installations, live show installations, ensemble performance, mixing into other music, applying tons of effects, etc.