What I do reckon is this - the image on the slide is the finished product. That is, if you want something black in the final presentation - which is to say, in a projector against a wall - it needs to be black on the slide, and if you want it white it better be white (well, clear.)
Which is to say, negative film lets you play fast and loose capturing a wider range than you'll print - you can decide in the darkroom through nothing more complicated than the contrast grade of paper you choose and the exposure under the enlarger how you want to compress or clip the captured range into the print. Slide film doesn't give you that luxury; so in practice whether or not the range is larger than printable the usable range is significantly narrower than negative film.
So I reckon it's not so much 'harder', it just gives you less opportunity to correct in post.
A slide in a projector though is indeed a lovely thing, my favourite form of photograph. I'd give my eye teeth for a medium format projector although I've never seen one (I know they do exist of course; ) my medium format and large format slides I view on the light-table. Of course I also (whisper it quietly) scan them.
A 4x5" large-format slide on a lightbox is a bloody beautiful thing to behold .
Printing them is doable though. I've printed a few Ilfochromes myself and they look outstanding, they have a wonderful depth to them - but it's a hellishly expensive process.