I very much prefer -- to the point where I'd say I extremely prefer -- cumming inside my partner. It's not a territory-marking thing. It's...more than that. It's extremely difficult for me to put it into words. I don't get off on the hyper-aggressive, hyper-macho "I own this hole!" attitude. I get off because I know that the partner I'm fucking (or getting blown by,) male or female, wants me inside their body. And furthermore that they want me to give them something of me that'll be there (and be theirs) after we're done and I pull out.
There definitely feels as if there's something sacred involved in cumming inside a partner, and -- for me at least, and I can't describe it adequately -- an important component of that is lost, if I cum into a condom or outside of them.
That said, if my partner doesn't want me to cum inside of them, that's it. No arguing. It's their body, so it's their choice, and not mine. (Rough play with a domination component excepted, when it's understood in advance. I'm neither into D or s, but I'll Dom, if my partner's really into it. I'm told I can be quite good at it, but when I do it it's because they crave it. I don't, particularly.)
So...yeah. It definitely makes a difference to and for me, but it's not a deal-breaker. If he or she decides not to take it inside, that's their prerogative. As to spitting it out, I don't mind if a partner does, but if they treat it as something disgusting, I do get insulted. I don't cum in someone's mouth if they don't want me to. Treating it as if I've just defecated in their mouth is just...rude. It's like going down on a woman and making all kinds of disgusted noises at the way she tastes or smells. (And to anyone insisting that pussy can't taste or smell rank? Oh, hell yes, it can. Especially if it hasn't been washed in a good while. Male or female, if you don't take soap and a wash cloth to that area, from time to time, it can get rank. Believe me. I've encountered it on both genders, and rank can be a deal-breaker. Although I'm polite enough not to make retching and gagging noises, no matter how rank it may be.) A little politeness and consideration goes a long way.