montrealer

There are indeed some great things about Mumbai, but I would also agree that for a first brief visit, Delhi is better.

More precisely, think of 4 main things you might be after
1) Historical sites, architecture, etc. - Delhi wins here IMHO
2) Pleasant upscale tourist atmosphere - restaurants, wandering, seeing "stuff" - Mumbai wins here - waterfront, kickass restaurants, wander around Kolaba, Bandra, etc. Delhi is too spread out for this, you have to go digging for individual stops that you plan out rather than set out to explore.
3) Cultural "safari" to the real urban city, see how most inhabitants live and make their living. You can do this in both.
4) Interesting day excursions - Delhi wins here as discussed above

vasantn

Delhi is boring except, of course, for the historical sites. I would much rather live in Bombay than in Delhi, but some of the fun stuff is difficult to do as a tourist on a short visit.

Your list brings back fond high-school and college memories: getting on the top deck of a double-decker bus, sitting in the front seat and riding to the suburbs and back just for the fun of it, or driving around in the wee hours grazing on street food!

I haven't been back in 25 years, but I guess some things never change.