A Standard account has one cost: the spread. On EUR/USD it starts around 1.0 pip and there is no commission. A Raw account shows the market spread, which can be zero, and charges a fixed commission of 3 dollars per lot on each side, 6 dollars round trip.
Six dollars per round-trip lot is 0.6 pips on a pair where one pip is worth 10 dollars. So a Raw trade on EUR/USD at a 0.1 pip spread costs about 0.7 pips all in, against 1.0 on Standard.
The gap widens on pairs with naturally wider spreads and narrows on exotics, where the raw spread itself is large. It also matters what you trade: commission is the same for gold and for an exotic cross, but the spread saving is very different.
If you place a few trades a week and hold them for hours or days, the difference is small and Standard is simpler. If you scalp, trade the news or run an EA that fires dozens of times a day, Raw usually saves real money.
You can hold both. Many clients keep a Standard account for discretionary swing trades and a Raw account for their systematic strategies.