Getting visual feedback using a display might be important, especially if you are taking photos. That’s the reason why I bought the holux m241, you can get it on ebay for $65+$14 in shipping. In my experience as long as you are going for the cheap versions the differences aren’t that great. If you buy the more expensive models you will be getting better signal, but qualitywise my sub $60 receivers have all worked fine.
People are using iBlues, Forerunners and m241 on Openstreetmap, and I haven’t heard any complaint about them… If you are only going to log I don’t think it matters what you buy…