The difference between the two is unknown if that is all that appears on the labels.
'Paprika' (with no other qualifiers and without a source) probably means little. Were it of quality it would designate both. 'Sweet Paprika' only means something if it is from Hungary or Spain. No other sources have regulations designating what can be called sweet. Other sources might label a paprika 'sweet' but who knows if it actually is or not until tasted.
Hungarian paprika has 8-9 grades only two of which are generally available here--sweet and half-sharp . The very best sweet is designated Kulonleges. Sweet, but of a bit lower quality, is simply called 'sweet'--edesnemes. 'Hot' paprika of quality (eros) is designated 'half-sharp'.
Low-end paprikas are ubiquitous--the big box stores and supermarkets carry them. Many are quite fine for 'normal' use. Low-end paprikas might be from anywhere (not necessarily a big deal) but aren't often of high quality--the stems and seeds might be included when ground, the ripeness of the peppers might not be as important when picking, inferior peppers might be included in the grind with better peppers--that sort of thing, and their lower price reflects this. Cheap paprikas can be useful in rubs (they add bulk and color) and are fine to use in that way. No need to seek better paprikas for rubs as paprika's flavor does not withstand prolonged dry-heat cooking--regardless what quality they are. If you are looking to add chile pepper flavor to a rub use a chile that is more suitable to long cooking. But for bulk and color, inexpensive generic paprika works well.
If, however, the paprika is to be used in a shorter dry-heat cook or a moist heat cook like a braise (of nearly any length of time) then seek the best quality paprika as it will make all the difference in the results.
(Hungarian paprika does not have a 'plain' or 'regular' designation and, notwithstanding Cooking Light's imprimatur, Hungarian paprika without a designation of Kuhlonleges, sweet, or half-sharp should be avoided if one is seeking quality as there is simply no such thing as 'high-quality regular [Hungarian] paprika.' Were it of quality it would carry a designation.)