You can look at the AF website and check the availability of business award flights before making your decision. I recently transferred my Amex award points to FB. I was able to get excellent value on biz seats to/from Europe. I am new to both Amex and AF/FB. The miles required was clearly market driven - it quadrupled on adjacent flights/days. Thankfully, I this worked in my favor: SFO-FLR (my actual destination) one way business class for $475 plus 39,800 miles. (I could have paid more miles and less dollars.)
Still working on the return. This is nothing compared to United's $300-ish plus 170,000 miles for one-way!
I found the website extremely use-friendly. I am used to United and they make me work harder to find the value award fares. And the product does not compare...
I am going to Europe so I chose AF over KF. But I dream of flying Singapore First some day!!!!
Good Luck