1. The bigger the power, the faster the marking speed. 100w 70w 60w 50w 30w 20w
If fiber laser marking machine use the same field lens, and gain same marking effect, the bigger the power, the faster the marking speed. That means 100w 70w 60w 50w marking speed will be faster than the small 20w 30w fiber laser power machine. 

2. The bigger the power, the deeper the marking depth. 100w 70w 60w 50w 30w 20w
If fiber laser marking machine use the same field lens, and set the same marking speed, and marking power on the software. the bigger the power, the deeper the marking depth. That means 100w 70w 60w 50w can mark a bit deeper than small power20w 30w. 

3. Stainless steel, aluminum, iron ,ABS Simple marking within 110X110mm marking area, 20W is enough. 
If you want to mark stainless steel, aluminum iron, silver, gold, copper metal material and ABS plastic simply, without marking depth requirement. And its maximum working area within 110X110mm. 20W is enough, sure, 30w 50w, will be faster. And 30W 50W will be better for marking gold, copper, silver. So, you can choose according to your budget. 

4. Optional Working Area Field lens: 110X110mm 150X150mm 175X175mm 200X200mm 250X250mm 300X300mm The bigger the field lens, the longer the focus distance,  the longer the focus distance , the weaker the laser beam power. 
20W is suitable for 110X110mm, 30W is suitable for 110X110mm 150X150mm 175X175mm  200X200mm 50W 60W 70W 100W is stutable for 110X110mm 150X150mm 175X175mm 200X200mm 250X250mm 300X300mm.  It will be a bit different according to marking materials. 

5. Stainless steel Color marking by Mopa fiber laser marking machine. Mopa 20w 30w 60W
Mopa 20W, Mopa 30W, Mopa 60w can mark color on stainless steel. As for mopa fiber laser marking machine, 175X175mm is suitable for steel color marking. So, mopa 20w, 30w 60w can all mark color on stainless steel with 175X175mm filed lens. The bigger the fiber laser power, the faster the marking speed, that means Mopa 60W can mark color faster than mopa 20w 30w. You can choose according to your budget. 

6. Copper, Silver, Gold, Jewelry Cutting  50W 60W 70W 100W
Some cutsomer will use fiber laser marking machine for cutting thin metal, such as aluminum, copper, gold, silver, jewelry by repeat many times working.  Then 50W 60W 70W 100W can cut within 1mm by repeat working. If you want to use fiber laser marking machine to cut thin metal, then small field lens is stanard parts,such as 70X70mm, 110X110mm.  The bigger the fiber laser power, the shorter the cutting time. That means, if we cut same file, same metal, 100W cutting time will be short than 50w.