US TAXES - Online services vs advisor in Belgium

Dear all,
I recently submit a post asking for a US tax advisor in Belgium who doesn't charge an arm and a leg. Some of you answered (thanks!) suggesting instead the following online services:
www.greenbacktaxservices.com
www.expatprotax.com
H&R Block
www.taxesforexpats.com
I did a quick research and found some bad reviews about H&R Block while the site of "expatprotax" has expired. For what concerns "green back services" and "taxesforexpats", I found mostly good reviews.

Does anyone has personal experience with the above services?

Or, better, can somebody suggest a "cheap" advisor? As I am not a native English speaker and have no knowledge of taxes jargon, it could be difficult to deal with this subject only per emails or phone...

Many thanks in advance!