As noted above, US Military tracers, by design, should not light until at least 100m-150m downrange. That's to make it harder for the folks on the receiving end of the fire to track the tracers back to the source.
They are also significantly longer for the same basic starting weight. The M855 and M856 are a good example of this. 1 in 9" twist is actually the ideal twist rate to stabilize the M855 ball round. However the much longer M856 round requires the faster 1 in 7" twist to deliver the required long range stability to match the long range penetration required of the M855 ball round (steel pot at 700m). That fact is lost on all the tacti-cool types who insist the mil spec 1 in 7" twist is better on an AR shooting M855 and similar length rounds. It's just not and the extra spin from the faster twist exacerbates the accuracy issues with M855 ball ammo (although it's less of an issue in the M4 with it's shorter barrel and lower muzzle velocity - with commensurately lower rpm imparted to the bullet). One in 7" twist was a necessary evil to enable an M16A2 or M4 to stabilize the longer M856 round - something that is a very dubious capability at best.
The tracer round itself is designed to accommodate the area denial traits of the machine gun where dispersion is considered a good thing, so lack of accuracy isn't really a consideration, nor is the reality that the trajectory of tracer and ball rounds no longer co-incide at longer ranges anyway.
So...if you want to shoot patterns rather than groups, a tracer is not a bad way to go. Otherwise, stick with ball ammo.
In terms of M855 and M193 ball, both suffer from generous acceptance limits in terms of accuracy, but the M855 projectile with it's more complex construction and penetrator is much less consistent and much less accurate than the comparatively simple lead core and copper jacketed M193 projectile. Again it's a case of there being a performance downside to the improved penetration of the M855 round compared to the M193 round.
Personally, I think for general plinking and shooting out to 350m, the M193 round in a 1-12 or 1-9 twist barrel is pretty hard to beat.