Front panniers add stability to a heavily loaded bike with rear panniers.
For commuting, rear panniers are more useful and almost no-one uses front panniers on their own.
I use 25l carradice panniers for commuting. They are pretty empty for most journeys but the extra space is useful for shopping stops. Usually I just carry one unless I am on a weekly grocery shop.
Features to look for are
Flap top closure : quicker and more convenient than expedition style roll-tops and good for bulky items.
At least one external pocket.
Heel cutout shape so you can mount them further forward.
Quick-release locking mounts: quicker and easier then hook and elastic.
Stiffening on back and base.
Tough, stiff material with good weatherproofing.
Ortleib, Vaude, Carradice, Arkel are all premium brands that will stand years of hard use.
I put my lock on top of the luggage rack, not inside the bag.