Before we get to the composites portion, let me first ask you what type of decking you have now -- is it regular deck boards, or tongue & groove boards fitted tight together?
- If you have T&G I would generally recommend sticking with wood - as today's wood is not as good as past years you may consider going with Mahogany, IPE or something else that is very durable.
- One other great option which is mistakenly called composite is a solid PVC product like AZEK or TimberTech XLM.
If you do go with a regular style wood, instead of painting it, you might consider using a solid color stain instead (preferably sealing all six sides and any cuts).
Regarding the composite issues, yes there have been issues with mold in the past, particularly with TREX products when they had some major quality issues, but those have been dealt with. As for the claims and issues I would be careful in believing everything you read on them & take them with a grain of salt.
- With that, many manufacturers have varying qualities and yes you get what you pay for.
- Also they do need to be swept and cleaned every so often.
- Proper installation & care based on conditions will result in a deck that will last quite a long time.
For more information:
Read Sean's blog post Composite Decking Lawsuits & Issues.
Also, read "What are the best green alternatives to wood for decking?" a Q&A answered by Marian Keeler.