A 738 is 5% faster than a 734, uses ~15% less fuel, and has more range. So yeah, it's better. Whether it's better enough to justify the extra cost depends on your airline & gameworld. With fuel at $1000, you'll save about 180k/month with a 738. 14 million extra on the price tag costs you about an extra 180k/month in lease price. But if fuel is only $200, and you can get them much earlier, then yeah, the 734 might be a better choice for you.