I totally get you on STP brokers—they’re great for fast order execution without the hassle. Spreads feel more manageable than fixed commissions.I would go for the STP broker, because order execution is not a trouble anymore while you cooperate with such a company. ECN brokers usually don't have spreads, and they have commissions for trading, whether per lot one-sided or round-turn ones. I am not the adherent of commissions and prefer paying spreads as a type of fee, because commissions are usually fixed dependong on the lot size, while spreads vary.
Plus yeah, as I said, order execution is quite fast.