Prop Firm Spreads and Execution — What's the Real Deal?

Been trading with various prop firms for a while now, mostly in futures and some forex pairs like $EURUSD. One thing that consistently catches my attention is the significant variance in reported spreads and effective execution across different platforms. We all know the headline numbers they advertise, but when you're actually in the market, especially during high volatility, slippage can eat into profits quicker than you'd like. I've had situations where a firm's quoted spread looked great on paper, but my fills were consistently a pip or two wider than expected, which adds up considerably over a month of active trading.

This isn't just about the raw cost of a trade, but also the overall confidence in their infrastructure. Some firms seem to have direct access with deep liquidity, others feel like they're routing through third parties, adding latency and cost. Has anyone else noticed this and perhaps found certain firms consistently provide tighter effective spreads and more reliable execution, especially for scalping or day trading strategies? I'm not looking for specific recommendations to avoid shilling, but more about shared experiences and what to look out for when evaluating a prop firm's trading conditions beyond just the advertised leverage and profit split.