It has been argued that virtual sound environments can facilitate better assessments of hearing ability and hearing device benefit since measurements obtained in these environments more accurately reflect the real world. Several researchers have presented strategies for simulating complex acoustic environments and thereafter investigated the effect of transplanting speech tests into such environments. Broadly speaking, the speech intelligibility measurements obtained in the complex environments lead to different estimates of performance than the estimates provided with their standard test counterparts, and these differences are not yet well understood. In this study, we investigate these differences in a specific population of patients that are known to contain large individual differences, and we hypothesize that a lower-than-expected spatial speech-in-noise score (i.e., worse than expected in a complex environment based on the score in a standard test) can be explained by poor localization. Thirteen unilateral cochlear implant (CI) users who were implanted following vestibular schwannoma (N=10 with single-sided deafness; N=3 with asymmetrical hearing loss) were assessed postoperatively on their speech and spatial perception with and without their CI on their (1) localization ability, (2) spatial release from masking (SRM), and (3) speech reception threshold (SRT) in a complex, reverberant meeting room. Localization abilities and SRM for this patient population were in line with existing single-sided deafness literature. The residuals of a linear regression between the SRTs in the standard and complex environments were significantly correlated with localization ability, but only in the aided condition. On the other hand, neither aided nor unaided SRM was correlated with the regression residuals, suggesting that these tests may be measuring independent aspects of hearing. The findings shed light on the importance of uncovering the relationship between these tests in order to better understand how to increase the real-world relevance of speech tests that can be used diagnostically to give a more accurate representation of hearing ability.