While violin and fiddle are the same basic instrument, there are many variables.
Folk fiddler's sometimes use a different bridge with a flatter arc to play double stops and often use steel strings while some old school classical players might use gut strings. Both also use synthetic strings. Different string arrangements are sometimes used in folk fiddle.
Folk fiddlers tend to spend less on their instruments. While this isn't a given it's pretty common for a weekend player to play an intermediate instrument. Rolling around in bars and under pavilions at picnics in the rain isn't where you want to take a nice instrument or bow. These instruments often use lesser quality construction and lower quality woods. This can sometimes result in a less refined or tuned sound. Less projection and uneven playing across all strings. Low end beginner instruments from 200.00 to maybe 600.00. Intermediate instruments from 600 to as high as 5000.00. Classical players are demanded to have only the better instruments for their technique which often involves higher positions on the neck. 2nd, 3rd,4th and 5th positions. Folk fiddlers mostly play in 1st position and sometimes go to higher occasionally. Classical players often live on those higher positions. I practice at 2nd and 3rd positions. For anyone mocking up music for a fiddler this is something to keep in mind. To be accurate I would keep fiddle tunes on 1st and 2nd position. No higher.
Classical players buy violins beginning in the 10,000 dollar range for an instrument with large full time orchestra players 20-30,000 dollars for a violin is not uncommon. Getting above those prices the buyer is often paying for collector value as opposed to player value or both.
I have 5 violins. I only have one decent violin that cast me 3000 dollars. I have a couple that are in the 1500.00 range too. The 3K violin also has a 400.00 bow. Advantages of the better violins are more responsiveness, better sound, made of better materials,they stay in tune better, they often project a little better with less effort. You can tell a BIG difference between most low end violins and the better ones.
So to answer that question in a nutshell aside from all of the variables I mentioned. Classically trained violinists generally play on much better instruments than the average folk fiddler. You can tell the difference in the sound. Classical players who also play gigs usually have a 2nd instrument for those gigs, probably something closer to mine.
Here's a video of Kevin Burke playing in the Sligo tradition.