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After many hours at the eyepiece of telescopes of both sizes (and many others) under all sorts of skies, I've developed the strong view that the only thing that matters in answering a question such as the OP's is the exit pupil range that will be used most often. Forget f-ratio, forget aperture as absolute measures. A city dweller with great seeing might find a large aperture extremely useful if planets are their main interest. Likewise, a fast f/5 will show a very dark sky background even in the city when a 2.5mm eyepiece is attached to view small, bright targets.
Basically, when the exit pupil exceeds 4 or 5mm in the city, the sky background becomes unpleasantly bright. Below 0.5-1mm, your target becomes so dim in the eyepiece that you'll need to shield ambient light (of which you'll have plenty) to make it work. Between these values, you're sweet. Find out what type of target is your favourite, work out the power range needed, calculate the corresponding exit pupil range and select scope accordingly. Extended DSOs tend to look best at 2-3mm exit pupil, perhaps a bit less than 2mm if the sky is really bad.
Speaking of selecting - regarding 8" vs. 10", none of the above will matter much if that is all you are going to choose from. The difference in the field is so small that you need to see them side by side, or observe very specific features on your target, to know it's there. The 10" will show the same target, at the same brightness, 25% larger, or a factor of 1.25. Nothing more, nothing less.
Value for money: 8" wins. Want a little bit more reach, especially on marginal DSOs, none of which you'll want to observe from the city, get the 10".
$0.02
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