"standard Soundbuds" can you be more precise please.
Happy to help. Ideally you should wait for a review from someone who has both, as their advice will be probably better than mine.
I have the "Slim" and I like them, they replaced the older IE20 I lost in travel. The sound quality I like, the in-ear fit is comfortable, it does a good job of noise isolation (I spend a lot of time inside an aircraft). My only bug bear is battery isn't that amazing, but heck "slim" must cause some trade-offs. The feature I liked from the older IE20 (I think replaced with what is now called the Tag) model is turning on/off when you pull the magnets apart / together, i.e. the magnetic function did something, with the Slim they are only magnets, I must still press and hold the power button to turn on or off. Relative to the IE20 they do a better job sticking in the ears - I think that is the slimness, so lighter and narrower to keep inside the ear.
I am on work conference calls (Webex) a lot, say 4 hours / day average, and from others' comments they say the audio is excellent. I used two mobiles to call myself and alternate the muting to be able to hear myself, and when the cord is behind the neck I would say the microphone is muffled so when I want to use to speak I have the cord over the front of neck.
I own plenty of BT devices, the Slim particularly does a good BT over distance job, I can get quite some feet from my phone before I detect any drops. That was the biggest positive surprise.
I pretty much continuously when moving have the Slims around my neck (magnets!) and my phone in my pocket and combined makes a good system. Having got used to magnets to make a necklace with the IE20, I'm never going back.
Ideally, wait for someone who has both to give feedback before your decision. The "non slim" (whatever that is) may be better but I have no experience.