A "standard" 112 might be enough, but it depends on how loud you're playing, what tone you want, what rooms you're playing in and how often do you get FOH. A better 112 will be clearer, more defined and sound better whilst being able to go louder maintaining a better tone and are more likely to carry the room on it's own. 2 "standard" 112's will sound much better than 1 and 2 "good" 112's will cover any playing situation and sound fantastic in the process.
The only cons I know is that 2 112's will cost more than a 212. I'd keep an eye on the classifieds until something you want comes up.
The same comments apply to 210 cabs, except 1 210 would go a little louder than a 112. IMO a good 112 would sound better than an OK 210.
2 210's would still sound better than 1 cab. If you want to look at 115's, that's another area, but again the good ones will sound better and go louder.
A good 112, 210 or any 115 would probably be a 1 cab solution for most people. Buy 8 ohm cabs and you can add another if you decide you need the extra oompf. A good cab will make a good amp sound fantastic. IMO it's worth the extra to buy "good" gear.
Go and see some bands playing locally. Talk to the bass player and ask him about his gear.