Over the years I've ran the old genuine AI 223 magazines, accurate 223 mags, and mdt metal and plastic 223 mags, and in a couple oddball cartridges I use the Ruger scout 223 AICS mags.
Genuine AI were the smoothest and I still have about 6 early production ones in service but near the end of their production run they started splitting down the center seam, and the thick reinforced feed lips didn't fit in all actions (notably tikkas.)
Current favorite are the accurate mags. They're smooth feeding (but not quite as smooth as the genuine AI mags) and reliable, but quite long being single stack. You do have to file the front of the liners for longer OAL.
Next up for me is the metal mdt mags. About as smooth feeding as the accurate, a bit shorter since they're double stack / single feed, but in all 3 of my 223 bolt guns they are not as reliable as the accurate mags and occasionally have feeding issues.
Last up are the mdt plastic mags. They feed ok but are horribly "draggy" on the cases and require a lot of force on the bolt to strip the rounds out of the mag especially for the first 4 rounds out of the mag in every gun I've tried. I was hoping they would work better because they're fairly cheap on the black Friday deals, but they sucked to use so I sold them. I haven't seen many others complain about this so maybe I got some bad ones where the plastic blend or surface finish was off.
Ruger also makes a 223 AICS mag for their scout rifle with longer feed lips than any of the other 223 mags on the market, but they don't actually feed 223 in any of my R700 pattern actions I've tried; the feed lips hold into the case too long and the cartridge enters the chamber at a weird angle stops the bolt; even worse with 223AI. Keep in mind the Ruger scout in 223 may use an AICS pattern mag but it is not an R700 clone action, so that's probably the reason; it was made for the Ruger action. However, the extra long feed lips on the Ruger scout 223 magazine means it works fantastic for reliably mag feeding the stubby little 20 vartarg in an R700 pattern action, while neither the AI, accurate, or MDT 223 mags would do so.