I've owned bumper pulls and goosenecks. Currently own 4 GN's, one 5th wheel (camper), and NO bumper pulls, and I would never consider owning another one. It's that big of a difference in how they pull and handle. Period. End of story. There's a reason why all semis are pulling 5th wheels, rather than "bumper pulls"........... it's WAY safer, because the load doesn't get leverage on your truck. The weight is placed just ahead of the rear axle (so in the middle of the frame of your truck), and some of the weight is then placed on your FRONT axle as well as the rear, and THAT is what makes it handle so much differently and more safely. No more headlights pointing at the sky.
Unless all you're hauling is light loads up to "car weight"... like 4000#, don't even look at a bumper pull.
And like BirdDog above said, "Trailers are like work shops. You always wish you had a bigger one.
Get the big gooseneck if you have the truck to handle it. Unless your tractor is toy size you will never be happy with a bumper pull."
Have you ever overloaded your current trailer? I'm betting you probably do every time you haul a load of hay. It's not "how much can you fit onto it"... it's how much weight is it rated for. My lighter trailer probably hauled 70% loads that were over it's rated limit. I bought it to haul hay, and every load that I hauled was over it's rating. There's a reason why they have "weight ratings" on them.... they're designed to haul up to that limit SAFELY.
You can always leave some of the bed empty.... but it sucks having to make another trip because you can't fit it all onto one load, or having to hire the haul done because you don't have enough trailer to do it. You get used to the length of the trailer that your pulling, and a longer trailer actually trails better than a short one does. Once you're used to it, you'll never wish you had a smaller trailer, guaranteed. That being said, I've got a 14,000# 30' GN with manual dovetail and flip over ramps, and a 25,000# 34' GN with hydraulic dovetail (this one too has been significantly overloaded... biggest load had over 50,000# of LOAD, not including the trailer.... NOT GOOD!!!!!, and I went really slow, and only had to go like 15 miles with it).... I like that lighter trailer when hauling lighter loads, like my skid loader, because it's faster to hook up (don't need the low speed on the jacks), and I leave the dovetail down all the time on it, and then just flip the ramps to load/unload. If the big trailer was just as easy and fast to hook up and load/unload though, I'd sell the light trailer. Hydraulic dovetail is nice, but another thing to go wrong and have to maintain, and the ramp then ends up being steeper (no flip overs to extend the slope)... and that's a problem when I get snow/ice on it... can't always make it up, I've never had that happen with the smaller trailer with the flip over ramps.
BTW... my wife just walked in and asked what I was doing..... ME: "A guy on this forum is asking if he should get a gooseneck or bumper hitch trailer".
WIFE: "Oh my God... what a stupid question!" I asked what else she said.... she said, "There isn't anything more to say".
As for the picture of the jackknifed gooseneck posted by chevy taHOE5674 above, yeah, it can happen... but it'll absolutely happen alot easier and DOES HAPPEN alot more often with a bumper pull. Usually, with either, it's driver error... going too fast, with an improperly loaded load, or a load too heavy for the trailer or the truck. Also, I've got a dually pickup, and I will say that those help for truck stability too. B&W hitch is my choice, hands down.
TaHOE also commented that "5th wheels don't have any oscillation.... so not good off pavement"... that's NOT the case with a gooseneck... they're two entirely different attachment systems, although they both place the weight of the trailer where it needs to be.