Ah this is an interesting one.... glad it came up, as it's something I've been thinking about, too.
I'm a SAHM with 7 month old DD and DSS (13) and DSD (10). I hate to say it, but I really do feel unequal since stopping work, and I'm not even remotely high-achieving or career-driven.
DH doesn't treat me in any way unequal, but it's how I feel, and I really hate feeling that way. My maternity pay runs out soon (not that there's much of it) so DH will be giving me 'spending money' each month, but I'd far rather feel I was earning it myself.
I know there are plenty who would say this is nonsense, and it's not 'mine/his' but 'ours', but there you go....
I'm not even sure where I get this attitude from, bearing in mind my mum was SAHM with part-time jobs only when we were older.
I'm just telling myself that, as others have said, these things shift over time and this is just the situation we are in NOW, so in the scheme of things it doesn't really matter.