Quality and guarantees.
As Mechie said, you get what you pay for. If you're just starting out (I assume), start with a small imported (from Asia somewhere) breadboard. But this thing won't last very long and begin to get intermittent and difficult to use. If you're intending to get hot and heavy into breadboarding, I'd purchase a larger, high-quality breadboard. The two brands that I recommend are Global Specialties and E&L. Both are American-made and both have an UNLIMITED LIFETIME WARRANTY. If your breadboard should fail to give you complete satisfaction (it gets intermittent or even if you've wrecked some of the holes by using wire that was too large or melted a section of it with a hot resistor or reverse-polarity IC), just return it to the manufacturer post-paid and they will send you a new one. It's that easy. I've taught electronics for 20 years and have worked with these breadboards day and and day out, specifically maintaining a covey of about 50 E&L "Pencilbox" digital trainers. Whenever the breadboards on those trainers showed too much wear and tear, I'd remove them and send them (sometimes 30 at a time) back to E&L and they send me a like number of new ones, no cost to me other than the postage to send the bad boards in.
I prefer the Global Specialties breadboards over the E&L breadboards if I had to choose. Their geometry is better with regard to the supply rails with 0.1" between rails while the E&L boards have 0.15" between the rails, which is odd. Both have Interplex Electronics as the parent company, so probably doesn't matter to them which brand you buy.
Not only do you get the guarantee, but the Global and E&L boards last a lot longer than the imports and can take a lot more abuse.
Dean