Proposed Canon
A unit's stats(also called statistics or points) are a set of whole numbers that describe it's abilities. Each unit has five knowable stats and at least two hidden stats. It is unknown if units with special abilities may also have additional stats.
 Visible Stats
Move: A measure of a unit's ability to travel across the hex grid. Units have their move reset to its full value at the beginning of their side's turn; unused move reverts to zero at the end of the turn.
These can be known, but are not instantly known by all and may take some reasoning.
Upkeep: Upkeep is a cost paid by Rulers to maintain Units.Erf-b1-p039 Certain units, such as Decrypted, have no upkeep.Erf-b1-p145 Upkeep has not been described as a stat, but it is a value that all Units have, even if zero.
Loyalty: Although the result of Natural Thinkamancy, Loyalty is expressed as a unit statistic. However, the value any unit has is unknown. That value can be altered by Thinkamancy such as a Suggestion Spell. It is probable that loyalty is subjective and is different if different sides are involved.Erf-b1-p084a
Experience: Experience is a statistic theorized to exist that explains why units level. A measure of the amount of combat a Unit has participated in. This statistic increases as the Unit croaks enemies. The value of this statistic is hidden from other units and even from the Unit itself.
Score: Determines one's fate in the afterlife. Also a measure of one's accomplishments in life. Score is a debated matter of conjecture in Erfworld, akin to a theological argument. (Although it's existence as a matter of conjecture in Erfworld is quite certain to the readership.)
 Possible Stats
It is possible that Units have other non-visible stats or stats that are only relevant with certain special abilities.
Juice: How many spells a Caster can throw in a Turn without resorting to Scrolls. Since there are several instances of Rulers asking Casters what their juice level is, it is likely that if Juice is a Stat, that it is NOT a visible stat.
Intelligence: Obviously not everyone has equal mental abilities. It's also possible that people's mental abilities are more quantifiable on ErfWorld than Earth.
Luck: May be a sort of "natural" magical stat that may change over time and affects all units to some degree or another. Random events may be biased in favor if those with higher luck stats. Can be a positive or negative value.
Love: May be a sort of "natural" magical stat that is shared between two units and may change over time. Affects how units feel about each other and affects the decisions the make regarding each other. Love, like luck, could be a positive or negative value.
Weight: Resistance to force and gravitational pull. The only implications we've seen are the ability (or lack thereof) to mount another unit.
Immortality: If the Titans do allow some Units to have a life after death in the City of Heroes, there must be a Stat which measures how much progress a Unit has made towards being admitted to the City. One of the other stats, like Level or Experience, might be used to determine this, but it may have a separate stat, if winning isn't everything. Some Units, like Wrigley, never achieve level or experience, but still hope for immortality.