Hi,
a lot of posts have been put forth for similar question, but here is what applies to you in short,
- you are not from a visa-exempt country, so a visa is required, and you know that already. However, when processing your spouse's visit visa, one thing that the VO will look at is the applicant's ties to her home country and the ties to Canada. Your wife will have a very strong tie to Canada, ie. being married to you, so her ties to Bangladesh need to be very strong (house, family, job, school, etc.) and you need to prove that to the VO. Otherwise they might think that she has no intention to leave canada at the end of her visa, and refuse it. a letter from her employer stating that she is getting a leave of vacation and that she will be gone for X weeks and that she will be resuming her employment on date XXXX would work, so would if she had a business or house in bangladesh, etc. the family ties sort of balance out, since her husband would be in canada, so you do need some other strong ties to show that she will be coming back to bangladesh. in my opinion your current idea of getting a visa and then apply for PR once in canada will most definitely result in a refusal of the visa.
- if you do an inland application, then the applicant cannot leave canada. if they do leave canada, and then are refused re-entry for whatever reason back into canada the PR application is denied since it is considered abondoned. versus in the outland application the applicant is expected to be outside of canada so can freely travel but will need to be in bangladesh if an interview is required. an appeal is possible for outland applications but not in the inland, if for whatever your are denied initially. for inland you need to enter canada legally, and the chances of getting a visit visa for a newly married spouse dont' seem too high.
one suggestion that i have seen on this forum is that after you apply for your outland sponsorship (ie means apply via bangladesh, which is covered by singapore) you can make a sepearate application for a visit visa, again showing all the ties to home country, and that she will be returning and proving that and also including proof of your PR application and explaning that you don't want to jeopardize this PR application so that is even more proof of you not wanting to overstay. however, this is also at a slim chance since the VO may still assess that your wife will overstay her visa and not leave canada.
i just had a glance at the singarpore timeline (26 months) and i feel for you (my wife had to go through islamabad which is at 28 months), but remember that these timelines are for 80% of the applications. Looking at the breakdown for singapore (latest data is till sept 2012 only), they completed 50% of the applicants within 15 months. so keep strong, gather all your proofs, look at your application with a very critical eye and anythign that stands out as somethign that the VO might question address it right away. with straight forward applications the timeline could be less ...