ECN brokers should offer you tighter spreads and an overall better trading experience.
In a way, your question is not valid as STP brokers no longer exist in many parts of the world due to regulatory changes. Your only real options when choosing a retail Forex broker are ECN or market market.
Forex brokers are either market makers or pass trades to liquidity providers. ... STP and ECN brokers are fitting in this category. Before discussing the difference between STP (Straight Through Processing) and ECN (Electronic Communication Network),