As others have said, it's totally personal choice. Capsules and car seats are both safe for your baby so personal preference is all it comes down to.
No doubt the stroller salesperson said what they said because there are some really neat travel systems out there if you want to go for the capsule option. I really wish I had've considered this before my first, but we were given a car seat as a gift so it didn't really occur to me to investigate (plus the travel systems are much more prevalent now than 4 years ago!)
We coped fine with just a reversable car seat, but I must admit I had capsule envy when my friends at playgroup brought their 2nd kids in a capsule, placed them in a quiet corner to continue sleeping and went about playing with their older kids.
There are plenty of capsules now that can safely take a baby up to 8-12kg, so I think it is possible to get your money's worth - especially if you then have more than one kid.
Having said all that, if you see a stroller you really like or just simply can't afford a travel system (the good ones are really quite exey) then get the stroller you like and think about car seats later.