You want to buy window boxes or planter boxes, and you have read all about the different options. There are wooden and wicker products, which are classic, beautiful, and reasonably priced, but they rot, crack, and break easily, meaning you will have to spend money to maintain, repair and replace them as needed. There are vinyl products, cheap and readily available in different shapes, sizes, and colors, but they look like toys and typically need to be replaced annually. There are wrought iron or steel cages, stately, grand, and sturdy, but they are heavy, more difficult to install, and limited in sizing and design. Finally there are PVC window boxes and fiberglass flower boxes and you’re trying to decide which one really is the best. A lot of that depends on your vision and purpose for the final outcome of your window box or flower box garden. Both are going to be much longer lived than any of the other options. Both will be more of an up front investment than the wooden, wicker, and vinyl options, but will outlive those options for a better long term investment. Both will have more sizing and color options than the wrought iron options and the PVC option will be less upfront investment.
So how do you decide? Fiberglass window boxes are a molded product, so you are going to see piece to piece without seams or general weak points. However, fiberglass is suited for indoor use as cold temperatures can cause freezing and cracking while PVC has thermal movement that allows it to be installed indoors or out, and survive the heat, and the cold without needing to be brought in or winterized. The molded nature of fiberglass means that custom sizing is often either unavailable or requires large orders as they require new molds that are expensive and require a large investment to be worth creating.
PVC flower boxes are hand built by a craftsman to your specifications. PVC, not to be confused with vinyl or polypropylene, is cut from boards and sheets and therefore can be built to custom sizing without large upfront investments or new tooling. Painting fiberglass requires a lot of prep work and specialty set up, while PVC can be painted with a brush or roller and standard high quality exterior latex paint. PVC planters come ready to paint and don't require any additional sanding or priming or any special tools.
Both materials have a longer lifespan than other products, so which will last longer? Both will claim that they have the longer lived option and tell you that their product is the master of time so who should you believe? The answer is, Both of them, just read their warranties and trust them to be honest about their own product. Fiberglass companies typically offer a 3-5 year warranty on their products. Flower Window Boxes, offers a lifetime guarantee.