I have worked at a few companies some i love and some i hated, some big some small, but one thing that rings true to all off them is any employee is replaceable.
It is harder to find work i agree, but i think the answer to what is a better option is very much decided by the individual involved.
I for example think life is too short to play it safe, i wanna take shots and make something big of myself.
Many may disagree and say that stability is as the core of their needs and do the same thing for a decade slowly climbing the ladder if they are lucky.
I think outside factors also influence how you think about a career... are there people depending on you for money ? a family ? or is it just you... do you have support if your risky career moves fail ?
As for the question about big and small companies, the way i see things is that the world is shifting to a bigger divide in small in rich companies , same as the rich and poor , bigger companies are killing or absorbing smaller compnies everyday.
Now as a individual you can decide im going to work for a small company help build it up... so you throw the dice when it gets absorbed you will be dropped or praised for being somebody who is a stalwart and should be on-board with the merge.
If you are in a big company going up is tough i think, because of competition of internal politics and a general less attention to individuals as the reason behind successes, but i think you are a little safer there career wise.
I could be wrong i dont think every big company is the same or every small one the same so again everything is based on individual circumstances.
There are no solid answers to this.... is anything in life certain anyway.