that number is the spine. the 350s are like 1 GPI heavier i believe.. its said that a heavier arrow is generally quieter...but you gotta worry about spine...thats the most important thing. bad spine=useless arrow
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Whats you draw lbs?, that would help to give you an answer too.
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The spine of the arrow is the biggest difference. It really depends on your setup and what you are wanting to do with the arrow. If it is a hunting arrow then the added weight can be an advantage. If you are looking for speed then you don't want it.
I would look at the chart and attempt to match the correct arrow with you setup. Poundage and drawlength.
I have a 28" draw on my Tribute and started out w/ 350's and they were way toooo stiff. I could not get it to tune and shoot to my liking so I licked my wounds andthen bought a dozen 250's. They are shooting amazing and tear nothingbutperfect holes in paper.
It is ALWAYS safer to stay with an overspined arrow vs. an underspined arrow. At 28" shooting 70#, you should be shooting a 350, until you drop to 63# or less, the 250 is underspined.