There are two main types of synthetic lifting slings:  Polyester round slings and Nylon lifting Slings.  Both have their own pros and cons.  But most importantly you need to take into account the operating environment, conditions, stretch under load, and the workers difficulty of the lifting load. 

• They are not as durable as chain slings when it comes to cuts and abrasions.
• They have a low heat resistance and are not recommended in high heat applications.
• Should NEVER be used if it will come in contact with sulfuric acids or alkaline.
• Can’t be used in environments in excess of 194°F or below -40°F

Nylon Slings:  Nylon Slings, like polyester round slings, are versatile, and can be used vertical, choker, and basket hitches. 

• Very popular due to their multi-purpose uses. 
• They can be fabricated with wide widths for heavy and large loads.
• 8-10% stretch at rated capacity – can help reduce shock loading, but should not be used when elongation is not intended.
• Strong for heavy loads yet will not scratch or mar your load.
• Nylon web sling performance isn’t affected by oil and grease

• They are not as durable as chain slings when it comes to cuts and abrasions.
• Can’t be used in environments in excess of 194°F or below -40°F
• Should never be used in alkaline environments.

Safety notes:  Never overload.  Never exceed the working load limit.  Avoid shock loads. Be sure to identify the type of resistance required for your application.  Always inspect slings before each use.