It really depends on your regular playstyle, do you tend to use one shot weapons and are effective at weaving in and out of cover in between shots because the crossbow takes forever to reload, and also has inherent bolt spread and drop. If not I'd go with the riot shield.

Also I'd just use the regular bolts if you go with the crossbow all of the specialized ones increase drop and reduce one shot potential. In fact I can't remember which one it is but either thermite or explosive literally can't one shot someone using bomb squad in the head

Personally I would have a much easier time with the crossbow as I have been grinding one shot weapons lately, and that for adjustment nerf they added to the riot shield is just nasty literally unplayable for me.

I do have to second the other comments and ask, why exclude the pistols?

They are fun, most of them kill faster than half the smgs and a couple are downright broken, even more so with akimbo