Don’t assume that all synthetic cabinets are an improvement over wooden panels.  Plastic panels from cheap brands tend to fade, craze, warp/buckle and crack more easily and sooner than wood.  Also, it might be impossible down the road to find a replacement panel if one of them is damaged.  Even if you succeed in finding one, the colour will almost certainly be off, due to dye lot batch changes and the fading or your old skirt.  Very often, paint will not stick to synthetic cladding when exposed to the elements. 

Even cabinets made with high-end synthetic materials aren’t always better than wood.  In some cases, the synthetic slats are held together by gluing or stapling them to cheap pressboard on the back, which can swell and rot in wet climates.  The individual slats themselves might stand up to environmental attack, but the whole panel can fall apart when the pressboard behind it deteriorates due to humidity.  These panels may do just fine in California or Kelowna, but are NOT good for Vancouver weather.  

Years ago, wood cabinets were standard, and synthetic skirting was an upgrade. Assembled tongue & groove slats was the norm for synthetic skirting, but solid single-sheet stamped panels are becoming more common. They’re cheaper to make than wood now, but that’s not necessarily a bad thing, as long as they are substantial and made of good materials.  

Hot Tubs with removable panels have a huge advantage when it comes to finding and fixing leaks.  Some brands have stapled and glued-on panels that cannot be easily removed, so you have to cut into the skirt with a low-plunge blade to create holes in the cabinet in order to find the source of the leak and access the plumbing.  This can damage the structural integrity of a hot tub and will leave ugly scars.