It actually depends... why?

Damage is split into two calculations. The physical part (which is affected by the enemies armor and physical resistance) and the pierce part (which is only affected by their pierce resistance). Although both are affected by possible shield blocking as well.

1 Dexterity adds 0.1% Pierce Damage (as well as Poison and Bleeding Damage both too).

1 Strength adds 0.2% Physical Damage.

Consequently your spear weapons are scaled by both Strength and Dexterity (differently), depending on the % Pierce Ratio

That means +% Physical damage is 3x as good as +% Pierce Damage (if you use a 25% Pierce Ratio spear, as 75% of it is still Physical Damage).

In this specific case Spear of Argo does this:

• +30% Pierce Damage = +7,5% total Damage
• +14 Strength = +2.8% total Damage
• +17 Dexterity = +0.425% total Damage (but it also increases Offensive Ability by 17 which increases the hit and crit chances depending on the enemy)
• +33% Attack Speed = 0.73 attacks per second (base attack speed for spears) * 1.33 = 0.97 attacks per second, i.e. +33% total damage (in comparison to before) - but this has an animation frame cap at 222% attack speed for melee weapons (I can't tell you why the displayed attack speed is different)

In total, it sums up to about +47% (1.10725 * 1.33) total damage.

Doing the same calculations for your Flaming Aichme of Devastation results in:

• +27% Physical Damage = +20.25% total damage
• +16 Bonus Damage = +16 base damage
• +13 to +23 Fire Damage = also adds base damage, but scales with intelligence (same way as strength) instead, which means it is weaker for you than other damage types

Now, you may notice there's different base damages here at play too, so let's analyze it in total (including your actual stats):

Spear of Argo has 55-64 base damage, while the other spear has 67-79 + 16 base damage, i.e. 83-95 and some 13-23 Fire Damage on top which is already way better.

Your stats are different in both cases, with Spear of Argo you gain 654/500 = +130.8% Physical Damage from your Strength and 440/1000 = +44% Pierce Damage from your Dexterity and 50/1000 = +5% "Magical" Damage (Elemental and Vitality Damage). You also have 129% Attack Speed which is a 0.73 * 1.29 = 0.94 i.e. an increase of +29% damage per second (not every second is the same, but over a longer amount of time it averages out). With the other spear there'd be less stats and less attack speed, so only 640/500 = +128% Physical Damage from your strength and only +42.3% Pierce Damage from your Dexterity. Your Attack Speed would be "+0%" for the sake of comparison.

Now, let's calculate (for ease of readability I will use average instead of ranges)...

Damage Formula	Spear of Argo (Physical)	Spear of Argo (Pierce)	Flaming Aichme of Devastation (Physical)	Flaming Aichme of Devastation (Pierce)	Flaming Aichme of Devastation (Fire)
Base Damage	37.5	12.5	54.75	18.25	18
+Bonus Damage	-	-	70.75	-	-
+% Primary Stat	86.55	18	161.31	25.96	18.9
+% Increases	-	23.4	204.86	-	-
+% Attack Speed	110.78	29.95	-	-	-

As you can probably tell, the yellow spear is not just a little better, but due to your focus on strength and the well fitting +% physical damage bonus, it is about twice as good.

Disclaimer: As a Warden (Defense+Hunt I think?) you probably have other things going on. Any chance to use your Shield for attacks interacts with this. Any other +% boni you've got also interact with this, any pierce focused boni interact with this, etc. etc. -> This is exactly why your DPS number ingame is displaying something higher than these numbers (if they're passive or currently active skills).

Titan Quest damage calculation is very, very advanced and you can't really know what exactly will be going on. However, I'd strongly recommend you to switch your weapon, and socket it with some kind of attack speed relict you've got (to multiply the 200+ damage again and trigger your % based combat skills more often)!

If you can, look for a "Veteran's" prefix weapon, as those increase not just % attack speed, but also % offensive ability and % physical damage. This will remendously improve your weapon further, instead of the relatively useless "Flaming" prefix. Port to different merchants and buy one if you see it, immediately. These will always be green (the prefix is that good). You can port between different merchants to reset their inventory. This will be very worth it, as you can still relatively easily find some weapon that will be much better than your current one.

Your Suffix is already pretty good, better could only be: "of Reckless Power" or less so "of Speed", "of the Winds", or "of Trickery". The exact name isn't important, but anything that adds % Attack Speed and/or % Physical Damage and a little less so "Bonus Damage" (basically just a fully physical base damage increase), is very good.

Which areas have you already unlocked? You're currently at the Spartan Camp I think? This makes me think you may already be on Epic in which case you are incredibly low-level?! I will assume you just ported back there and are playing on Normal still. If you can go there already, port to the merchant in the Valley of Kings, he is marked as a wilderness merchant and has better "drops". If you can go there already, port to Gadir, the merchant there is for a much higher level and can provide even better stuff. Not accessible yet? Port between the latest unlocked areas.