My PCs have a spear which is able to cast the Daylight Spell. Would this have any effect on Vampires in the spell radius like regular Sunlight would or would it just be considered Bright light for the vampire and have no ill effects against him?
The Daylight spell, unfortunately, does not count as Sunlight. In each spells description, it will actually mention if the spell counts as Sunlight or not, for the effects of creatures weak against it.
Here are two examples of a few spells that ARE Sunlight from page 279 of the Players Handbook (PHB).
Sunbeam: A brilliant beam of light flashes out from your hand..... Undead and Oozes have disadvantage......For the duration, a mote of brilliant light shines in your hand. It sheds Bright Light in a 30ft radius and Dim Light for an additional 30ft. The light is sunlight
Sunburst: Brilliant Sunlight flashes in a 60ft radius centered on a point you choose.....Undead and Oozes have disadvantage.....
Those are just a few I found. I believe one more exists, but I can't locate it. Note that there is also Moonbeam that adversely affects shapechangers (Which Vampires also count as) and counts as Moonlight.
The daylight spell may be named after the light of the sun, but its effect is what matters, and is specifically a sphere of "bright light".
Meanwhile, a vampire's abilities and vulnerabilities specifically call for "sunlight" — light from the sun itself.
It's not impossible for a spell to exist that does explicitly create light that is equivalent to sunlight, but daylight isn't that spell. Think of daylight as a magical lamp with a steady, bright light, rather than sphere of sunlight.