如果不计风险， 就去试试B啦， 免得心里记挂。 不过我是懒得折腾， 肯定就去A啦。

get the offer A. B's just a start (or not even a start yet). It's very possible you lose offer A while you are trying company B.

True. If you keep company A waiting, they may feel nervous/troublesome and just withdraw from the hiring. So grasp the sure thing first then pursue other options.

Don't know your field. But if the market is hot, my personal oppinion is that it's worth to try company B while let company A wait for few more days. It's very common and reasonable that you ask for some more time to arrange your own business before on-board. If a employer has made a committment to hire somebody, it's very unlikely they will change their mind just because you may start a little later. It's not that much fun for the hiring manager/HR to go through the interview-hiring procedure, either.

If you did very well with company B, you may push them to make a quick decision, by letting them know that you have offers already. Acturally, in this way, you may even get a nicer bargin if you are really good.