Neither of those are going to do very much to soften light outdoors where, more than likely, there's not going to be anything for light to bounce off.
The best option would be to find something to bounce off - e.g. get someone to hold a reflector and bounce off that. Failing that, a bounce card (the larger it is, the softer the light) which you can easily make yourself. I've used funkyfoam (from Hobbycraft) which works pretty well.