You can order the bullshark from Amazon but in the U. S. I think the only way to order a P35 is from Krale. They are not bad to order from, however.
The P35 barrel is 450mm, the bullshark is 490mm. Because of the longer barrel the bullshark has different baffles in the shroud and is louder, I think. Many of us are using printed moderators inside the shroud which eliminate clipping which can happen with the baffles. That requires sliding the shroud forward a bit, however. About 1.5 inches on the P35 and probably almost 3 inches on the bullshark. The bullshark comes with a threaded end plug for the shroud, however, so you can put on a normal 1/2 fine thread moderator. (Donny sells one that fits the P35)
The bullshark is about a pound heavier but still only about 6 lbs. Part of the added weight is the barrel but the stock is also heavier reportedly. The bullshark also comes with more variations in the stock which could help it fit you.
I think the guns are the same except for these things. Reportedly Carm magazines fit both. Xtreme airguns plenums fit both. Trigger adjustments are the same for both. A lot of P15 parts also bit P35s and bullsharks. P15 videos can help owners of the newer side cocking guns.
Snowpeak also has a P35X on their website which looks interesting. 530mm barrel and 65cc plenum. If you want power from a P35 it could be attractive. Also has a wood stock.