Radiance on the bear works normally, but basher/hypers is better for disabling enemy carries. But honestly- NEVER build AC on sylla, no matter how many "pros" you see doing it. AC is one of the biggest wastes of gold theres ever been. Make 2x hypers on the bear and an MoC on sylla if you want -5 armor, otherwise just get 3x hypers. AC is a very bad item made by cookiecutter players.
You can pay 2100 gold for 55% ias, which makes your bear's attack absolutely crushing, especially with a basher, or you can pay 3250 gold for nothing but +15/-5 armor. You don't need that. Thats not economical. Your bear needs armor like it needs a dagon- it don't; and -5 armor is *not* worth 3250 gold. Its a complete waste, and should never be done until your bear's inventory is completely full and so is sylla's inventory, at the 2 hour mark of the game. Even if you see a "pro" doing it; they're making a horrid noob mistake
Theres really only an assortment of items you can mix and match. You either rush radiance on the bear, or you don't get it, then you want bashers and mass hyperstones, in no particular order- not necessarily basher first, not even if you skipped radiance; a hyperstone open on the bear is not actually a bad idea in some cases, and a phase at some point. On sylla himself, you can get MoC, or vanguard, or heart, but honestly you can generally do fine with nothing but boots- some MU's might even call for a hood. But sylla has the highest permanent HP/armor of any hero, more than anything cept maybe alchemist with ult on, which isn't permanent, and about 20 less HP than centaur at level 25 but a bajillion more armor, so tanking items aren't exactly core.
Don't get vladies either, on either sylla or bear; thats even more of a waste of gold than AC.
Now I might disagree on when to use radiance vs basher/hyper straight on a bear with most people, since the changes to the metagame, emphasis on mobile carries, and the huge nerfs to radiance/bear without the ability to walk people down (more than once every 2 minutes), but some items that see common use, like vladies & ac, are just dumb
oh and yeah;
Depends on who you are fighting.
Is there a hero / Are there heroes you can dominate with Radi? (ex. Silencer)
Or is their hardest carry someone you need to bash to death? (ex. N'aix / Lycan )
Syllabear has the luxury of what I consider the widest range of available item choices of any hard carry.
Determine the situation and use them.
Indeed, for example if there is a naix in the game, do not attempt to get radiance under any circumstances and simply get nothing but basher & hyperstones unless you want to lose horribly and run away from every clash. Much better to just repick if you can, however, since you're still fighting an uphill battle
But if they're loaded with silencer, cm, and other squishy supports, get ur bear his shiny gold