I have two boys, 15 months apart, and I had quite an experience looking for a double stroller. I bought 3 duds and finally hit the jackpot with the fourth. I really wanted a side-by-side that I could use for shopping as well as walking and everything else possible. The first one I tried was a no-name cheapy that I found at a second-hand store. It had "small" wheels (not the jogger wheels) and was incredibly difficult to push and maneuver. It was too wide to get through some doors and I wanted a stroller I could use for shopping. Plus the foot brake was right were my leading foot stepped, so I had to take short steps to avoid it. I ended up giving it to a friend who didn't have a double stroller, so she gladly accepted it. But I'm surprised she remained my friend after using it! It really was awful to push.
The next stroller I got was a Schwinn double jogger which was much easier to maneuver but was still too wide and the seats were not clearly separated with any divider so my boys got smooshed together and my younger son really did not like that (he needs his space). Other than being too wide and the "mono-seat," it was a great stroller. Easy to push one-handed, easy to fold and put in the car, just couldn't always fit through doorways into stores. I got it at Costco and they are great with returns (I had it about 8 months before giving up on it).
Next I tried the Kolcraft Countours Options tandem. It's an impressive stroller but it did not work for me. It is extremely heavy, which I did not mind necessarily, but it was terribly difficult to get the right leverage to lift it into my SUV (I am of average strength), and going uphill with my boys in it was an incredible workout (which is a good thing, unless you're not looking to sweat all the time) - my boys were about 50 pounds combined at the time I used it. It was also very long, which I suppose is to be expected with a tandem, but I felt like my little one in the front was so far away from me, I just didn't like it. I felt like he was more vulnerable way out there in front (I'm sure that was silly of me). But the thing that made this stroller unbearable was that my boys hated the stroller. They fussed and complained almost constantly when they were in it. I don't know if it was uncomfortable (the seats are pretty shallow and don't seem comfortable) but whatever the reason, no matter which seat facing I used, they fussed. It made going for walks and shopping rather unpleasant. I had found this one at WalMart.com and promptly returned it.
I thought about the sit and stand, but I didn't think my oldest (2 years old at the time I was in the market) was ready for that. I considered several different tandems, but I didn't know how either one of my boys would feel about sitting in the back, plus I didn't like the length of the one tandem I did try. I thought about the Graco DuoGlider, but didn't try it. It have heard some other moms have been very happy with it.
I wanted something that would be easy to maneuver on different types of terrain so I could go for long walks, but not too big so I could also use it for shopping and fit through aisles without a problem. I decided to spend the big bucks and I got a Valco Baby Tri-Mode twin. It was quite a stretch for us financially but it is the best money I have ever spent. It is worth every hard-earned penny. I have had it for 11 months now, and I wish I had bought it when my second was born (he was 14 months old before I broke down and bought it). But, at that time I just couldn't see spending that much money for a stroller, nor did I have that kind of money laying around. It is a dream to push; I can easily push it one-handed on any terrain. It is only 29" wide so it fits through any doorway (even the small side door of my garage). It works great for shopping, walking or anything else you would want a stroller for. My sister-in-law has the Phil and Ted's front/back double stroller and we compared the wheel widths of our strollers - my side-by-side is only about 2 inches wider than the front/back, and the seats in mine are plenty big for my 3 year old and 2 year old (both stocky boys) - with room to grow. You can get an attachment for it so you can use the infant car seat with it, and you can buy snack trays now for the kids' seats (wasn't available when I bought mine, but I'm thinking about getting them now). My husband can take it jogging. It has great sunshades. And the best part is that my boys are happy in it!! I can take them for a 45 minute walk and usually have no complaining or fussing (they didn't last 5 minutes in the others). I got mine from www.babystrollershop.com. He throws in several free accessories (and free shipping).
Another note about the Valco: it is quite a production to fold it and it is not light getting it into the car (but not too difficult), my husband hates that part of it, but it is so ideal and perfect when in use, the folding up and storing complexities are completely overshadowed by how wonderful it is when I'm using it. I see it as 5 minutes of difficulty for hours of perfection. That's a descent trade-off in my opinion.
I would suggest trying some different strollers you are interested in and see how you like them. At least push it around the store (preferrably with both seats occupied, if possible). The high-end strollers (like Valco) are hard to find in stores, but if you're interested, I saw another mom respond on this website with info for a store she has in Orange County. You can rent their strollers for a day (that would give you a real good idea). The website is www.octraveltykes.com.
Good luck to you and congratulation on baby #2!