I've only used spendbitcoins and was happy with the service, largely because they were the first place i found to trade for cashing in without it taking 1/4 of my pathetic gains as a fee.
Looking at SBC and FC4BC right now SBC is offering $6.66 (eek) while FC4 is offering $6.44 (now $6.42), and deepbit tells me mtGox has it at $6.66 (was 6.69 when i started!! SELL SELL SELL!
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Based on a 10BTC transaction:
SBC = $66.60 * 0.956 (-4.4% fee) thats $63.67 in your pocket.
FC4 = $64.40, thats only $0.73 more, although i must admit i dont quite get your 'no fee' and 'effective fee' but any fee is going to end up being less value than SBC, no? unless the 'effective value' is their undervaluing of the BTC to their advantage, your expense?
From what ive heard from Jeremy @ SBC (emailed him a couple of times, seems friendly enough), its currently manually processed, and in the middle of automating it. I've had transactions done in a couple of hours, and others about 12h on, afaik they're aussie based (think he has someone state side too) so it could well be down to time of day its done. Call me fickle and shallow, but SBC just looks more professional, FC4 looks like someone knocked it up in 1hr. Im sure they're both respectable and fine, its just first impressions.
Cant comment on FC4BC as this is the first ive heard of them, someone else can shed some light on them