should I

[Refrakt]

Use higher ilvl agility gear with stats versatility / haste etc or I should stick with lower ilvl with multistrike etc?

Since MS is main stats compare to other stats before hitting 40%.

[ruga]

BrM? WW? For both there's suitable spec discussion threads available under the stickies.

For WW: Best answer is to sim it (http://www.simulationcraft.org/download.html), though Haste/Versatility are "ok" stats.
For BrM: Can't comment, sorry. Though higher ilvl also means higher stamina, something to consider.

[Kaylisto]

Use higher ilvl agility gear with stats versatility / haste etc or I should stick with lower ilvl with multistrike etc?

Since MS is main stats compare to other stats before hitting 40%.

Since you are saying MS is best stat, I assume you are speaking about WW.

The MS softcap is 59%, after this Tiger Strikes will push you higher than you want to go. Some people factor in weapon proc as well, some don't. Having Tiger Strikes and Weapon proc at the same time is actually less common than you'd think.

Generally speaking, the higher ilvl is better. Agility still does more for WW than any other stat. MS is only our best stat due to our attunement. Everything but mastery is pretty close in value. If your higher ilvl piece doesn't have mastery, you'd probably be safe to use it.

as ruga said above though, your best bet is to sim it and see the results.