Speaking as someone who works for an EA, there are a lot of things that EAs do that the onlines won't. It works for some people like eskinosekiss who want control, but it is not for everyone.
Things to think about:
Buyers don't always feel happy to be shown round by the owner / negotiate as you may be offended if they say "well we think the bathroom is dated and will cost £3k to replace" for eg, so some people would rather walk away than discuss it with you whereas the EA is a buffer and will act on your behalf.
Will you be happy with showing complete strangers around your house? Some people feel very vulnerable about this.
The buyers will have your phone number / e-mail address, are you happy to be telephoned at all hours / ranted at when things don't go to plan? For that matter are you happy to give out your contact details to all and sundry who may ask to see the house.
An EA will probably have a pool of buyers on their books that are interested in properties, they will know their situation and be able to recommend who is best place to proceed.
An EA will get all the buyers mortgage offer info, will you feel happy asking for this and will the buyer feel happy giving it to you?
Will you be able to list the property well and take good photos? A good EA will use a decent wide angle lens to take a shot of the whole room with decent exposure etc etc to make the most of it, snapping a pic on your smartphone won't do.
Could you maybe find a halfway house solution? Use an EA that will do the bits that you want them to and not the bits that you don't and will agree an appropriate fee?