I've shot a few rolls of both. IMO the 400 is a little too grainy, and unless that's the look you want it's a little intrusive. The 100 is pretty good for the price. You can get it from firstcall photograp hic pretty cheap, while your at it get some apx it's also good value and you can decide what you prefer
they look great to me so I've got to have a go with it now, ordered the 100
In case your interested these are my kentmere shots, the tags will say what speed.
http://www.flickr.com/search/?q=Kentmere&w=49248828@N06&ss=2&ct=0&mt=photos&adv=1&s=int