Hmm, I have quite a few boas now, and I honestly think all of them would make great pets. Possibly not first ones, but great nonetheless. Here's my take on the species I own.
1) Caulker Cay Boa. Mine is a baby male. This is a dwarf species. He is fantastic and very laid back and curious. He will hiss and be defensive when he wants to (He's only done this when I've tried to feed him frozen/thawed instead of live and he kept striking and missing, I guess he got frustrated.) All other times he's a fantastic snake, never strikes or bites. He's the one I take with me if I want to go to a petstore, or if I want someone who is scared of snakes to hold. He will wrap his whole body around your hand and just chill there forever. He lets you touch him anywhere, including his head. And this is all as a baby, he was like this from the start.
2) Bolivian Boa. I have an almost 4 foot male. He is, quite possibly, the tamest boa of all of mine. (Though I could say that about a lot of them, boas are so great lol) He's big, tame from the get go, perfect feeding response. I can also touch him anywhere, including his eyes. (I had to rub some mineral oil on a stuck eye cap, and he had no problem with it.) He loves to wrap around my neck and crawl down my back or on top of my head. He enjoys going outside and crawling around everywhere. Has never attempted to strike or bite at me, ever. He was like this from the start. This is a snake under the definition of "puppy dog tame."
3) Brazilian rainbow boa. I have a baby female. She was sweet and active right out of the package. She's a little more shy than my other boas, but is still friendly.
4) Nicaraguan boa. I have a young female. This is probably the only boa I have that I wouldn't recommend as a beginner boa, just because she is a little more wary than the others. She's never actually tried to bite me, but I am still careful around her. She will intently watch me and follow my movements, however, I do put my hand into the tub and stroke her, and she still won't bite me. She just watches, and she will put her face right onto my hand and tongue flick me. She was a little flighty when being held in the beginning, but after only a few handling sessions she stopped that and moves slow and curious like the others.
5) Jungle/albino/snow boa. (These are all BCI's) My jungle is male, albino is male, snow is male, and I have a female snow coming. All of these have fantastic dispositions. They are all similar in docile-ness, (Made up a new word lol) Active, curious, great feeders, etc. Once my jungle got a bunch of dirt in his mouth and he let me hold his neck, stick my fingers in his mouth and dig all the dirt out. They are all sweethearts.
6) Dumeril's boa. I just recently got this guy/gal at a local show, but I am super in love already. He is my first Dumeril's boa, but I am super glad I took the jump and got him. He's very very sweet, completely gorgeous, and such a nice feeder! He lets me watch him while he eats, which I really appreciate. Also (I don't know if it's just him or all dumeril's) but when he sits coiled up, he creates a perfect coil. He looks like a female sitting on eggs, that is how perfect it is lol. He's just so gorgeous and nice, he's a definite favorite. I have to stop myself from bothering him too much during the day because I just love him so much.
I hope this helped
Honestly my first snake was a ball python, but a boa would have been a better choice for me. No offense to ball pythons (Which I love and own) but the boas, there's nothing like them. It is very clear to me that boa's are my favorite snakes to own. The first boa I ever held was an adult male BCI, and I could handle him no problem (He is also the one who made me fall in love with them. He was a pet store snake and yet was so sweet to me.)