Fixed is NOT a good option, especially at 6.25%.

Why would you go with a fixed loan???
Do you intend to live in this house and never refi or sell?
The offer you posted is TERRIBLE!!!!!!
I don't recommend fixed for many. There are some excellent and versatile 'alternative' programs with payment options far superior to Fixed products.
If your goal is to pay your mortgage off faster than 360 months, an ARM could give you a huge head-start on principle reduction.
A $600k mortgage pmt @ 6.25=$3694
A $600 ARM PMT as low as $1999.51 for 12 months.
Making the payment you expect to have at 6.25% with another program would allow you to reduce principle monthly by as much as $1694.49!!!! (3694-1999.51=1694.49) ($1694.49 x 12 = $20,333.88 principle reduction in 1st year of mortgage- making the payment you are planning on.
Confussed?
fixed products are long term. If you plan to make 360 payments to your mortgage company & like the small amount of principle you pay at $3694 per month- fixed is good.
There are many misconceptions about ARMs.
The goal is to reduce principle owed as fast and as inexpensively as possible.
Good luck,
BriantheBanker