The Importance of ETF Execution

Eric from Sensi writes: Have you ever looked closely into the execution of trades on different platforms for retail brokers such as Schwab, Fidelity, Interactive Brokers, etc. Are orders filled with equal efficiency across platforms when buying and selling ETFs? Do you see similar price quotes and spreads across platforms at the same time of day? As our portfolios grow in size with age, the dollar value of our trades for buy and sell orders increases as well. If we in the risk parity community are not executing efficient trades, I imagine it could start costing us real money as our portfolios gain in dollar value.