Is a bmx bike or a mountain bike better for not well made, medium sized dirt jumps? (Im a beginner)?

mountain bike definitely won't be suitable... actually- what you meant by "mountainbike" there? if it's a free-ride MTB you can jump, sure. but it will cost you a lot of money, LOADS of money. you can buy a good bmx for less than 1200 bucks. and of course,- there are dirtjump bikes which are specially made for jumping dirts :)

for that price, a bmx dirt jumpers, new, start at around 800$, unless you want a really crappy one.. while with a bmx, 400 will get you a fairly nice bike as for the jumps, how well made they are.. if the landings are flat and bad, 20 inch bmx wheels are stronger If they're really rough, 26 or 24 inch mtb wheels roll better I'd just work on em and make em nice and smooth. Both will work fine. Also, a lot of its personal preference I ride dj with an mtb, i really am not comfortable with such small bmx bikes my friends all ride em with bmx though, and really don't like jumping with mtbs. lol again, for your budget though a bmx will be much better UNLESS!! you manage to snag a decent dj bike used for that price. its possible .(i did) check ebay and craigslist literally every day if you really want a dj mtb over a bmx. It'll pay off and for clarification for other answerers... there ARE such thing as dirt jump mtbs!! examples blk mrkt .357 http://www.pinkbike.com/photo/1653812/ specialized p.3 http://www.specialized.com/bc/SBCBkModel.jsp?sid=07PBikes

you should get a bmx bike its good for dirt jumps just dont buy a cheap one

I answered one of your other 5 almost identical ?'s.

Well, it depends what you want to accomplish. BMX bikes are really light. I think redline makes a good BMX bike. Thats what my son uses.

You could use either type of bike.....just be sure to get a durable one with strong wheels. If your jumps are smallish on the approach and ramp, you might like a bmx better. Or, make them bigger with more dirt, and go the mtb route. Personally, I prefer jumping on 26" wheels, but either one is good. For your price range, you'll find lots of bmx bikes, but really nothing durable as a mountain bike. You can get an entry level mtb hardtail for that, but it's not jump-worthy. HOWEVER.....Jenson was running a psycho deal on the Jamis Komodo 1.0 freeride hardtail....complete bike for about $340 I think. They're sold out already, but you might check with them soon to see if any get returned. They do still have the Komodo 2.0 for $565 if you can spend a little more. Check it out.....it's great for jumping and abuse. I have one that I built up from a frame for urban drops. It'll take some abuse and the frame is definitely worthy of upgrades and replacements down the line. http://jensonusa.com/store/product/BI306A01-Jamis+Komodo+Fx+20+Bike+05.aspx Have fun!