Why not - add a mate's hdd, add a card; graphics, tv, sound etc without your own wants can leave you pulling down quite often without cleaning.
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As for the question raised.
I've not used a modular supply so can not compare, but my hard-wired supplies have handled my abuse as well as the power company's for some years.
I've not used a modular supply but hope they last as good as the hard-wired supplies I have. As for better; I think the term is lost in the question. I would think a modular supply would be better - on wiring and specifically on aesthetics. Sure the cabling would be tidier and less of a spiderweb, but would that equate to better quality? I doubt it but expect the fact the box and cables pull apart, you may find some companies pick better hardware for tails and such because they expect you to play with it all.
The plain hard-wired psu's include the bottom of the range supplies too, hence the lean in quality being lob-sided....nothing really unusual, just the English language words and sales pitches helping you miss the obvious......we all fall for it I'm afraid.
Edit: grammar