What's the difference in these lamps?

Beside $96? Both are 250 watts. Both are EVW. Both are 82 volts. Both have dichroic reflectors. Both are GY5.3 bases.

https://www.bhphotovideo.com/c/product/253054-REG/Beseler_8108_EVW_Lamp_250W_82V.html

https://www.amazon.com/Replacement-Halogen-9100-2010-Overhead-Projector/dp/B07NXMQ6MD/ref=sr_1_3?crid=3BPRBUX8SOL4Y&dchild=1&keywords=evw+bulb+82v+250w&qid=1614901836&sprefix=250w+82,aps,204&sr=8-3

Only one of them is available to order from Canada. (I can't order the second one through Amazon.ca)
The Beseler version is probably a top rated version, with profit margin to match.
The lower priced bulbs are less likely to be extremely consistent bulb to bulb, or to have the same relatively long life.
If you are doing volume production work, and need to have bulbs that allow you to do repeat prints at various times without seeing much/any variation, then the more expensive bulb may make sense.
@DREW WILEY would no doubt recommend an even better version, at appreciably higher cost.
I would be more likely to buy the cheaper option, but one thing I've learned, is that you always need to buy enough enlarger bulbs to ensure that you always have replacements at hand.
So don't buy as many as you need immediately - buy enough to have replacements too.
By the way, if that 250W bulb is one of the choices available, and there are other, less powerful options, you might consider them instead. A high power bulb is important for large (> 16x20) colour enlargements. Moderate enlargements from black and white don't need quite as much, and the lower heat produced is an advantage.

If you search for EVW at B&H you'll find a variety of bulbs from $6 up. I'd try the $6 first and see how it performs--at that price, you can afford to try it. The Beseler bulb isn't build by Beseler, so they have to add their profit (and it's priced as a spare part, meaning high cost for them and high profit) plus B&H's profit.

I wonder about the blades vs pins at the bottom. For a holder that needs blades, pins won’t work

EVW bulbs are common, and it's counterproductive in my opinion to risk a junk one when something high quality costs just a few more dollars per bulb. But don't buy ones privately labeled and reboxed for Beseler or anyone else, because it will be marked up dramatically (like over 2000% in the link noted prior!). Sites like Amazon are not likely to carry anything of real quality, nor are local stores. Go to a specialized online bulb supplier and get the real deal at reasonable cost. I buy either Japanese made Ushio bulbs or new old stock of domestic US made GE (GE no longer makes bulbs, but plenty still seem to be around; don't confuse these with their own imported cheaper line - two completely different marketing divisions.) There are also good EU-made versions. Don't buy cheapo Chinese bulbs, no matter the brand label. Good bulbs seem to last about ten years apiece for me, the discount type, just a few months at most. Maybe that's why some of you need so many spares on hand! - false economy.
And when those junk bulbs do blow, they sometimes spew crud inside the enlarger or pop in tandem with corrosion of the contacts, since the prongs on those kinds of bulbs are themselves inferior. Some of you probably spend more each morning on a latte at Starbucks than a decent EVW bulb costs from a specialty bulb house. In lots of 6, I paid about 7 bucks apiece for them last time - real deal Japanese Ushio. Might be up to around 10 bucks apiece now, but still reasonable.