just to warn you this is a very long message!!
i personally was in exactly the same position as you two years ago, i had no idea whether to do IB or A levels, so i posted a message on TSR and a lot of people told me to do A levels not IB, but i ended up deciding to do IB because i physically couldnt decide what subjects to do...when i started, there wasnt a single subject i didnt want to do, obviously now ive been doing them for a year and a half i have my favourites, but that will always happen.
taking the IB was the best decision of my life - i love it because i much prefer the syllabus to the a-level ones in most of my subjects, for example in english you do a lot of international authors on top of traditoinal things like shakespeare and john donne, and i've found them way more interesting than like frankenstein and paradise lost etc which the a level do. also im applying for languages at uni so studying international literature has been very helpful for that. i also love my history syllabus, which is all focused on the 20th century which is much better for me becuase i honestly couldnt give a damn about henry VII and spain in the 1400s which is what my a level friends are doing. so look closely at the syllabuses for the subjects because at the end of the day that is what you'll have to be studying, and it will be so much better if its something your actually interested in.
there is also very little difference in depth of detail - i;ve found that what im doing in maths (SL) and chemistry (HL) is the same level as A level, apart from the odd thing, but that is genuinely only the odd thing. also, the breadth you get can be very useful. a lot of people who want to do medicine think A level is much better than IB for it, but a good friend of mine does IB and has applied (and been accepted at Kings College) for medicine, and she does three sciences, maths, and also has english skills and good foreign language skills too thanks to the IB, which has given her a big advantage.
in terms of workload, i honestly dont think i have any more work then my friends (most of whom are a level students). the thing is, it comes in waves, so some weeks you'll have hardly anything, and some weeks you'll have a lot of deadlines, and that will usually be the time when a level have nothing so it will seem like more than it is
but remember that when they're all going mental because they've got AS's, you wont have exams. and my last exam, therefore when my summer holiday starts this year, is 16th may, more than a month before the last A level exam, so another bonus there!! most of it basically good time management.
higher level is more work and more topics, but thats why you choose higher level subjects you are a) good at and b) really enjoy!
i dont think its more work to get the equivalent of a BBB, i actually think its less - in terms of UCAS points, 45 points at IB is the equivalent of 6 A*s at A level. also, i think im in a much better position in terms of uni offers because there's a much bigger range of offers unis can give than with a levels. for example, i have two offers at the moment (for german and management) from southampton and warwick, for 34 points and 36 points respectively, and im predicted 44, so i could drop 10 points (which will only happen if i die in the middle fo the exam or something basically) and still get into uni, whereas if i had done a levels my offers wold probably have been AAB and AAA, so i could drop only two grades and not get in. so i think its much better. also you get your results a month and a half earlier than a level so more time to sort out problems
as you can probably tell im very pro-IB so no i dont regret taking it, i absolutely love it. and before someone asks, yes i do have a very good social life! i go out more than my a level friends. and i get at least 8 hours sleep a night. if you want to be successful doing IB then pick subjects wisely - make sure you know exactly what's on the syllabus, pick HL subjects wisely (only take english HL if you absolutely love love love it and dont take higher level science unless you may study something either maths or science related at uni), make sure you put sleep before anything else because ultimately, if your dying of exhaustion you are basically useless, and also, if you havent already, talk to the ib coordinator at wherever your looking at because what makes the difference between having a good time and a bad time at IB is often how good the coordinator is.
i am literally so sorry about the length of this, but you made me talk so....
hopefully this helps anyway!