The fact that this question is being posted on a website for blind iOS users means that you should already be able to hazard a shrewd guess at my likely answer. However, before we head towards that seemingly inevitable conclusion, I should begin by acknowledging that the answer is always going to be heavily dependant upon comparative levels of knowledge and experience. So, if given the choice between an experienced iOS user or a novice, you should probably always go with the former, regardless of any differences in their visual acuities.
There are a number of other caveats, assumptions and conditions which are also worth getting out of the way early on. The first - if the app in question isn't accessible with VoiceOver ... well, with the best will in the world, I'm not going to be the best person to ask how good it is. I might argue that its inaccessibility makes it an extremely poor app, but that opinion won't be based upon how good the app is at actually doing what it's supposed to do or how satisfying is the user experience that it provides in the process for the majority of its users.
There are also apps in the App Store where style, appearance or visuals are more important than functionality, and again I'm not going to be the best person to judge their merits. But, I would guess that apps where style and visual design matter more than function are likely to be few and far between. Or, perhaps I only believe this to be the case because these aren't the kind of apps, unsurprisingly, that I go looking for.
This doesn't mean that I believe interesting and imaginative visual design doesn't matter. It doesn't matter to me, but for mainstream users it will have some bearing upon the overall user experience. I'll compare this to reaching into my kitchen drawer for a utensil, when my hand will invariably be drawn towards those which feel like they have been designed with passion and vision. Although equally suited for a task, the more utilitarian options will sit at the back of that drawer, untouched and unloved.
However, despite acknowledging that the visual aesthetics of an app can improve the overall user experience, I also have to argue that my lack of awareness or appreciation for these things means that I am not easily distracted by them. Unlike the crying baby, I'm not going to be pacified and satisfied by somebody simply waving a shiny object in my face. Or, in this case, the app developer who wants to show off their visual design abilities.
And, now, we are finally getting close to an answer to my original question. Once all of the above disclaimers are accepted, and I sit back to explore and use an app, I do believe that having to rely on VoiceOver places me in a far better position than most sighted users to judge whether that app is actually any good.
I won't be distracted by any eye candy, and the nature of my exploration of the app and its features can be described as almost forensic in nature. I'll spend time exploring the interface with my finger, and with the aid of VoiceOver (assuming that the developer has provided concise and helpful labelling and hints) I will form an understanding and appreciation that probably goes far beyond that of most sighted users. Using VoiceOver forces me to think about each swipe and tap, and question whether this could be more efficient and effective. Is this the quickest way to get from A to B? Does each step along the way make sense? Is it a satisfying user experience?
What I am trying to say, is that as a blind user, I can't rely on a quick glimpse at the screen. I need to explore every pixel of the screen with my finger and VoiceOver to be sure that I locate all that is present, know what everything does, and therefore appreciate how satisfying or frustrating the user experience is.
I have no hesitation, therefore, in concluding that using VoiceOver gives me a thorough appreciation and awareness of the quality of an app's interface, its functionality and the overall user experience. Would a sighted user be able to say the same? In most cases, I doubt it.
I would love to hear if others believe that VoiceOver makes you a better judge of the merits of an app. Or do I simply possess an over-inflated opinion of how I use iOS compared to my sighted peers?