I have bought at these auctions but not sold. As dereko has said I'd think that most EA would charge a higher fee and you are limiting your sales market with Bidx1.
If you think your property will be attractive to cash investors then you are probably OK with Bidx1, if you think it's going to be more attractive to owner occupiers with mortgage approval then maybe not.
If you want a quick sale Bidx1 will also be suitable, if you are in no rush then the traditional method may be better.
Having been involved in these auctions there is definitely an element of gambling, both for buyer and seller. Setting the reserve is crucial for the seller, too low and the property could go at that price, however alternatively a low reserve can generate interest and with multiple bidders there can be massive increases to reach the selling price.