I don't think it matters how you try to enter the country - if you're going through passport control, they will run your name and date of birth against the same database - whether in the airport or driving across the border.
If you're unable to enter Canada due to a criminal record, there are still two legal options left to you:
- You can apply for a "rehabilitation". The process means you'll need to spend the next 5 years without a conviction before they'll let you in - but it's the most likely method to succeed.
- Alternatively, you could apply for a tourist visa and request an exemption. The chances of it being successful are slim, but they may work if you need to travel in emergency situations (family member unwell or passed away).
I also wouldn't recommend testing out the system to find out whether you can sneak in.
I can assure you that the US-Canada border is well manned, and the searches and procedure you'll have to go through before you're eventually refused and turned back simply aren't worth it.
If that's not a deterrent, check out this page of reviews from people that have been hassled or harassed trying to cross this border: http://gocanada.about.com/u/ua/faqscrossingtheborde1/Border-Crossing-Horror-Stories-Share-Your-Border-Crossing-Horror-Stories.htm
So many "horror' stories... Makes you realise they won't hesitate to waste your time and make it difficult for you if you attempt to cross into Canada despite a previous conviction!