Well if this is Hank Pym as Giant Man, there are some significant differences between the combatants.
Strength: Giant Man's strength at maximum size (100') only matches up with Strong Guy's base line strength - both are around the 50 tonne mark (on the Marvel scale). However Strong Guy can ramp his strength upwards dramatically through the absorption of kinectic energy.
Durability: Strong Guy's absorption ability does permit him greater protection from kinectic damage but Giant Man still has significant resistance to physical blows, having engaged the Hulk and Iron Man in combat in the past. Both have less durability to energy type attacks (flame, electricity etc).
Movement Speed: Giant Man has the advantage here thanks to his size - having increased his base movement speed by a factor of roughly 16 times (at 100' tall).
Fighting Ability: I would be tempted to give this to Giant Man due to his long years of experience.
Intellence: Pym, as Giant Man, is far smarter than Strong Guy, so he should be able to come up with a winning plan (drawing on his many years adventuring experience).
Other Factors: If I remember correctly, Strong Guy has to get rid of the kinectic energy he has absorbed within 90 seconds or he faces more pain and further body distortion. This could prove a problem as Giant Man has greater movement speed and can hit and move off. Strong Guy is also near sighted and relys on his glasses. Smashing or removing the glasses would be a serious blow to his being effective in this fight. Finally, if this is Hank Pym from later in his career he also has the ability to project growing and shrinking fields without the use of further Pym particles. Therefore, he could just simply shrink Strong Guy and imprison him or work out a way to kill him (burning him to death or the like).
So if this is Pym as Giant Man then Giant Man for the win.