Couple things, DM shouldn't plan your dive. You should be doing that yourself. They may give you information, but you should be taking all of that in and doing the work yourself. A DM pointing at one of those comically oversized tables to a bunch of people with a mediocre understanding is as worthless as skipping it entirely. Some DM's give great briefings and you really don't do much. Most give pretty poor briefings and you should be doing much more planning.
It's been mentioned before, your computer is doing real time tracking of your tissue loading whereas a table will only do your deepest, or if you've got a Wheel, a couple levels. It will (assuming it's functioning properly) always have a more accurate representation of your tissue loading and thus your decompression status. The displayed NDL info, while different based on which algorithm it runs, will always be based on the information you feed it, when settings such as mix, altitude, etc, or information gathered from previous dives. A table won't give you all of this, especially once the first dive has you full of gas. Remember you always get deepest/longest with a table and that's all you get, no credit for shallower time, etc. Theoretically, more conservative, but people have still been bent on tables, even recreational ones.
As for algorithms being conservative or liberal, it's all a fallacy. People think a liberal setting "gives" you something, when in all actuality, it does nothing of the sort. Since tissue loadings are entirely theoretical, computers and tables give their best approximation. Your body may be entirely different. If tables drove your decompression status everyone diving the IANTD air table would be getting bent while the guys diving the USN table for the same depth would be fine since it "gives" you more time. Well obviously that's not the case. An extra minute over your NDL does not automatically mean you're going to get bent, leaving 5 minutes early does not mean you're going to get back on the boat free and clear. Bent is bent regardless of how many NDL minutes your computer was happily displaying as you were turned into a pretzel.
You hear about "undeserved hits," well really they're few and far between. Most often it comes out that there is some other factor that plays into it. Undiagnosed PFO's is a big one, people doing stuff like freediving during their SIT proclaiming, "I was just snorkeling!" Point is, whether it's a table or a computer, it's an approximation built on theoretical models that may or may not correlate to your body on any given dive. Again all you can do is have the most accurate information available and use it to mitigate the risk of decompression stress as much as possible. I hear lots of, "well this one gives me more time!" Ok, well be sure to tell that to your computer as you're sitting in a pressurized tube for 6 hours.
As for your computer specifically, the Suunto's are fine computers. They will modify the algorithm used to calculate an NDL based on several factors. Rapid ascents (unfortunately that could be moving your arm too fast too), SIT's shorter than 1 hour, reverse profiles, sawtooth profiles all reduce the amount of displayed NDL and increased STOP time once it goes into deco. If you follow what your computer tells you, theoretically you should be fine.
Bottom line, trust your computer, but realize no matter how conservative you dive, there's always the chance to get bent regardless of what you're using.
