We don't own the Buck. We use the O2 Revolution and the Vixskin Johnny and Maverick. Here are my thoughts:
Vixskin Johnny - at 1.75" the smallest of the 3, but still larger than the 1.5" toy you use. It's soft and comfortable for penetration. The head is defined - but not as much as the Maverick. The curve is also nice for P-spot stimulation. The balls also make for a nice thrusting handle. Because the shaft is a little soft - and not too long, it doesn't work as well for pegging - but it works fine when used by hand.
O2 Revolution - with it's bulbous 2" head, entry can be a challenge unless you are properly prepared. We use the tapered Champlette for preparation and it works fine. The O2 is by far the best for pegging. It has the firmest core and enough length. But the real secret is that it tapers down from the head. This adds comfort by allowing your sphincter to relax after initial penetration - while keeping that very full feeling inside. The reverse taper also prevents the sphincter from pushing the shaft out - as happens with the softer Johnny and Maverick.
I'm new to the Maverick - my secret goal is to be able to use the Outlaw. The softness of the Maverick substantially mitigates it's large size. Because the head tapers it's a little easier for initial penetration - but still requires the Champlette for preparation. However because the Maverick continues to get larger the deeper you go - it has a stretching effect quite different from the O2. I just wish that it was a tad firmer - making it easier for my wife to thrust. I'm not sure if the Buck solves this problem - but I know the Outlaw does, when I get the courage to ask my girl to strap it on!