Don't ask the bike shop what they think, they just think they want your money.
As for first big bike, don't get the 1000, it's a rough engine that's leaned out too much due to emission regulations. The clutch chudders (shudders and vibrates) on many and they are even heavier than the 650 with the same brakes as the 650, which aren't all that good if you are two up or when you need to do slow speed manoeuvres. You're much more likely to drop a heavier bike with a pillion on the back than a lighter one. You'll be wanting to upgrade the fork springs and rear spring if you ride a lot with a pillion if your pillion is anything over 6 stone.
That's unless you can get one that's had it's fueling sorted and doesn't have clutch issues, both easily fixable even if they haven't been done. The weight can be managed by using a lower seat and possibly lowering the bike (if you're vertically challenged), the spring upgrade is not a big issue, and the brakes can be upgraded. You can get all the advice here, but it's better knowing that there might be things that need doing than finding out after you've bought it. On that note, only buy a Vee that's got an adjustable screen, the chances that you get serious buffeting is good and you and your pillion will hate it at anything over 40mph. At least with the one that has an adjustable screen (K4 onwards) you can fit a Madstad bracket and sort it out.
The argument that you can overtake easier on the 1000 bike is valid if you're always in a hurry, can't be bothered to plan ahead properly and 5 minutes shorter journeys is worth a significant drop in MPG (queue big bike riders getting angry
) Two up I don't want to be in a hurry anywhere, I'm happy to over take when it safe, not because I can tear arse past everything easily, and I don't really care if it takes a bit longer to get where I want to be.
Warts and all, so you know what to look into before you get talked into buying a 1000 too easily. The 650 is by far the most popular bike for many reasons.