The Selle Italia is popular, and many people find the cutout section helpful. But other people's experience, while interesting, is of only marginal use when selecting a saddle because what works for one rider is anathema to another. For example, I tried a Specialised Toupe racing saddle for a while on the advice of a friend who raved about its comfort. It cut me to ribbons.
Lots of people complain abut the Bontrager, however, so if I were a betting man I'd wager that the Selle Italia would suit you better. It's just guesswork, though, and you need to bear in mind that as a new cyclist with only a few miles on the bike, it would be very surprising of you found the saddle comfortable. It takes a couple of weeks, and rather higher mileages, before the "sit bone ache" goes away. However, you have the right idea in thinking about the perineum. If the ache is over your sit bones, that is fine and to be expected. If the soft tissue between your legs is hurting, you need to adjust your position on the bike so that you can sit properly on the wide part of the saddle. It's a saddle, not a seat, one sits on it rather than in it, if you get my meaning. If you have someone who knows what they are doing and can look at your position on the bike, that's a god idea.
As for working into it, there doesn't seem much wrong with your approach. A gradual increase in time on the bike until you are feeling comfortable. After that you can cope with bigger increases in distance. Because cycling is non weight-bearing, there's no real need to restrict yourself to the runners' formula of a 10% increase in distance per week. Once you can comfortably ride ten miles, you're quite likely to find you can cope with twenty.