Only you know your workflow and what works for you. I agree that it is not advisable to make this decision based on what others do. Be that as it may I will give you my opinion.
If you are going to use Lightroom to its fullest capabilities then it might be a good choice. If all you are using it for is a RAW converter then I would opt for Photoshop. The conversions between ACR and Lightroom use the same RAW engine. The difference is the user interface. I have become used to ACR and find it quite easy to do multiple conversions, sync changes, etc. Lightroom has a nice pretty user interface and if that makes things easier for you then choose that. If all you are ever going to do is a basic RAW conversions and resizing then Lightroom is a reasonable choice.
If you are interested in doing more complex selections, component replacements, text or the multitude of other things to your images then CS5 would be a good choice. I am high on CS5 over Lightroom 3 basically because I was in the beta program and saw the performance and capabilities first hand.
None of these are intended to sway you either way. In the not too distant future you will be able to download the trial for Photoshop CS5. I would go that route and see which one works best for you the way you work, not the way others use the products.