Have you read the ammo Oracle on this site? Download the pdf and read the whole thing (google: ammo oracle pdf)
Then be honest with your self about what you are going to shoot. If the plan is to shoot 55 grain bullets then get a 1in 9" twist barrel. The only reason not to is if you are planning to shoot heavier bullets exclusively. As you stated before you are not. The only way to really make an informed decision is to become informed before you make the decision. Everyone on the internet has an opinion, and often these opinions are not based on any real knowlege or research. Many of us have had good luck with 1:7, 1:8, 1:9, or even 1:12 barrels; that doesn't mean that the decisions we made were right or wrong. My personal bet is that you will only shoot anything heavier than 62 grains a couple of times and all things being equal a 1in 9" twist will be optimum for you. But please don't take my opinion read what the researchers have to say...
This is what the ammo oracle has to say:
Q. What twist rate do I want for my rifle?
Probably 1:9, but it depends on what kind of bullets you intend to shoot.
Special purpose rifles often have uncommon twist rates. For example, if you are
building a varmint rifle and want to shoot the short 35 grain, 40 grain, and 50 grain
bullets, a 1:12, or even 1:14 twist would be best. On the other hand, long range High
Power shooters often select 1:8, 1:7.7, 1:7, or 1:6.5-twist barrels to stabilize the long 77,
80 and even 90 grain bullets used for 1,000 yard competition. Additionally, new testing
of heavier rounds (68-77 grains) seems to show that they perform very well in simulated
tissue and may be a better defensive choice than 55 grain or 62 grain rounds. The
majority of shooters, though, typically shoot bullets of 50 to 69 grains in weight (note
that the 62gr SS-109/M855 bullet is as long as a 71 grain lead core bullet) and should
select 1:9 twist barrels. At typical .223 velocities, a 1:9 twist will stabilize bullet lengths
equivalent to lead-core bullets of 40 to 73 grains in weight.
1:12 twist rifles cannot stabilize SS-109/M855 bullets and 1:7 twist rifles are slightly less
accurate with lighter bullets and will often blow apart the thin jackets of lightweight
varmint bullets. The 1:7 twist is used by the military to stabilize the super-long L-
110/M856 tracer bullet out to 800 yards, but unless your plans include shooting a
significant amount of M856, the 1:9 twist rate is better suited for general use.
There is, of course, an exception: if you want to use loads utilizing the heavier, 75-77
grain match bullets currently used by Spec-Ops troops and other selected shooters, you'll
want a 1:7 twist barrel. Although military loadings using these bullets are expensive and
hard to get, some persistent folks have managed to obtain a supply, and will need the
proper barrel twist to use them. Anyone who foresees a need to shoot this ammo should
consider a 1:7 twist barrel.