Horses are much more long term imho (guess it depends).
I own cars, I own horses.
We buy BLM Mustangs, and the atitude around here is that they are "trash horses" so we often get them cheap or free (we have had some incredible beautifull horses delivered to us from hours away because they thing mustangs are trash). Initial horse ownership is cheap, anywhere from free to 60K (gypsy/freesian(sic)). Ongoing costs are somewhat high. We pay $40 a month for hay, my wife feeds everyday (so we don't pay board). You HAVE to work with the horses every couple of days, or else they will quickly cause problems riding. Shots every year are around 40-80 depending on what you need. We spend ~$35-$60 a month on grain and supplements. Saddles can get spendy quick (we haven't spent much, we have 2, and have only spent $250 total). Tack isn't much, but adds up. Figure for CHEAP (non leather) stuff around $60 a horse (mostly one time). More like $120 for premium/show stuff. Trimming hooves (we go shoeless on all ours) is $30-$50, and you do that 3-4 times a year. Shoes are (iirc) $50-$100, and you usually get one pair a year.
A horse can't get you hundreds of miles a day, and is a lot slower. A horse needs fed at least once a day (we do 2 feedings). A horse can get hurt easily, and then it gets REALLY spendy.
Overall, a car costs more up front, but long term a horse is a HUGE commitment (but well worth it...)