C/C++ bitfields versus bitwise operators to single out bits, which is faster, better, more portable?

I need to pack some bits in a byte in this fashion:

struct  
{  
  char bit0: 1;  
  char bit1: 1;  
} a;  

if( a.bit1 ) /* etc */

or:

if( a & 0x2 ) /* etc */

From the source code clarity it's pretty obvious to me that bitfields are neater. But which option is faster? I know the speed difference won't be too much if any, but as I can use any of them, if one's faster, better.
On the other hand, I've read that bitfields are not guaranteed to arrange bits in the same order across platforms, and I want my code to be portable.

Notes: If you plan to answer 'Profile' ok, I will, but as I'm lazy, if someone already has the answer, much better.
The code may be wrong, you can correct me if you want, but remember what the point to this question is and please try and answer it too.