1.5 degree :shrug:
The difference will be in the degree of ease of steering. The 3 will be easer to steer than stock, and the 4.5 will be even easer than the 3. It has to do with the distance that the front tire is moved forward to obtain the difference in trail from stock which in turn reduces the effort to physically turn the wheel while it is moving at different speeds. The more the rake (greater trail) the easer it is to steer to a point. Handling to some with a 4.5 seems twitchy and overly sensitive, but with time they get use to it, and don't notice it. I think that the 4.5 is the most common. There are up to 6 degree steering kits available. Those are mostly used on the longer Trike Kits like the Trike Shop.
The difference will be in the degree of ease of steering. The 3 will be easer to steer than stock, and the 4.5 will be even easer than the 3. It has to do with the distance that the front tire is moved forward to obtain the difference in trail from stock which in turn reduces the effort to physically turn the wheel while it is moving at different speeds. The more the rake (greater trail) the easer it is to steer to a point. Handling to some with a 4.5 seems twitchy and overly sensitive, but with time they get use to it, and don't notice it. I think that the 4.5 is the most common. There are up to 6 degree steering kits available. Those are mostly used on the longer Trike Kits like the Trike Shop.