I like both, as well. There is no "one over the other", you gotta do both.
The strange thing is, people that go to Bonaire come back with similar experiences. You may go to one resort or stay at one place, but most folks get out-and-about and see the other AI's and cat around a bit. Driving a rental car there is safe, easy, fun and a requirement. They get to see a general picture of Bonaire.
Roatan visitors rarely get more than a tunnel vision view of the island, like through the slits of venetian blinds. People come away from the island with startlingly different and non-meshing recollections of the diving and surroundings. Renting a car and driving is simply a bad idea- the roads suck, there are no trauma centers and your accepted and absolute liability as a foreigner is paralyzing. Hired drivers are a bargain.
If you want lots to do other than dive, Bonaire wins hands down. Lots of beautiful beaches, good exploring, good roads, and lots of restaurants to try. The restaurant thing? That puts Bonaire in roughly the same trick-bag as Roatan. Most Bonaire visitors rarely venture past the main town of Krinkydink. They have no clue of the wondrous "joints" that only the locals venture into. After all, where else can you find Real Indonesian Rice Table (Risztaffel) ? How many visitors manage to find it? Very few.
On Roatan, if you are staying on the "West End", that's what you understand and know. You believe that the diving there is the same as the South Side, and you don't have but limited access to that, so- you really don't know. There are multitudes of great bars on the west End to watch sunsets with a cold Salva Vida in hand. Party central. On the other hand, many divers who stay at the AI's on the South Side- they have no clue as to the two superb restaurants that are hidden in the jumble of the West End. Instead, these South siders prefer and usually wind up at one of two S Side restaurants that are distressingly milquetoast. But South side divers know the wondrous little critters that Roatan is truly and best known for. Again- you only know what you know.
The shore dive opportunities on Bonaire are its greatest attraction. Most "house reefs" are rather mucked-up, but with a short drive, you can dive the best Bonaire has to offer. There is no more crime on Bonaire than any other Caribbean rock, it's just that dumb divers leave their valuables locked up in their cars. Take nothing other than dive gear, leave your car unlocked- money and drivers liscenses are waterproof. Again- no worse than any other Island, just increased opportunities due to the attractive shore diving.
I have been diving on every side of Bonaire (and some of the inland caves), and I absolutely understand the synchronicity of Klein Bonaire- how this smaller islet off main Bonaire is used to "hide behind" at dive moorings to find relief from the omnipresent SW convection oven blast of hot dry air. this is the picture book "desert isle" with cactus, donkeys and scorpions. Bonaire has some stunning dives.
There is no reason to dive the windward side (if the winds let up from the WSW to allow it) other than to say, "See my logbook?", yet it holds a great attraction. Skip it. Spend hours in the lush walls of the Klein Bonaire dives instead.
On the topic of Roatan divers only having that narrow view of the island, I'll give you my take. As much as I love the diving on Bonaire, I will take one resort's shore dive on Roatan hands-down over all of what Bonaire has to offer. Give me the "Front Yard" at CoCoView. No one sees this dive other than CCV divers. Certainly no-one at any other resort or lodging, not even those from across the channel at FIBR. Having done them all, I'll tell you that this "Front Yard" with the Prince Albert Wreck is a rare gem. Roatan visitors are exposed to a very limited view, but like most of us, we know "it had to be the bestest vacation ever". Consider taking a look around.
Still- there's not much to do on Roatan other than dive. It may be the last of the Banana Republics, but in fact it is the original and first Banana Republic. (This has nothing to do with clothing for teenage girls, Google "United Fruit Company" and you will understand). You have to take into account what people are really saying when they describe their ideal vacation spot. Are they really bone-head Nitrogen junkies... dive-dive-dive? Or are they hiding the fact that they might want to drink (more than) a few beers? In the Bay Islands, drinking is a practiced profession, in Bonaire, tourists may engage in what is still regarded as a sport.
Bonaire has those bays perfect for windsurfing, inviting touristy restaurants, topless environments, bars scattered about. A tourist's dream built slowly and artisticly from the many years of Cruise Ships coming nearby to Curacao, many years of monied divers from the US, many years of wealth Dutch tourists. Roatan is beginning this journey, but it got the green light last week (comparatively). Think Beverly Hillbillies on speed. Go to Roatan to dive or do the Margaritaville thing. Pick your resort, AI, lodging, or dive op with extreme care according to your true needs and desires.
Roatan has some attraction, But- after a while, you get tired of Bay Islands "steak", maybe wanting a little Bonaire cuisine as well. It's all good- but in Roatan, most folks only know what they know. Visitors to Bonaire have a much broader perspective, and in fact, Bonaire is fairly much the same, resort to resort. You really can't go wrong on Bonaire.