For me its more what is best for the wood. I consider what I do a craft. While a water borne sealer may look okay it does nothing for the wood in terms of conditioning. Most water borne sealers are loaded with acylics that cannot be stripped off. Below is an exceprt from
http://www.woodsealants.com/articles/why-wood-weathers.html
"For wood, in most southern states, the sun is Public Enemy #1. The sun is directly responsible for the intense drying effects leading to cupping, curling, cracking, splitting and surface checking. Water-borne treatments do little to alter these natural processes, but some are effective at controlling mold and mildew. Therefore, oil-borne treatments are recommended since they replenish wood oils that have been oxidized by the sun or washed out by the rain. Proper high flash point parraffinic oils (the new industry standard) are not only oxidation resistant, but also do not contribute to wood flammability (a consideration mainly for wood roofs). Though somewhat more expensive, oil-borne treatments are recommended over water-borne materials because of their superior performance. Wood is the pipeline for nutrients. The wood fiber is basically a series of straws that shrink and grow with moisture loss and absorption. By absorbing oil, these straws tend to regain part of their original size which reduces internal wood stresses as well as the volume available to be occupied by water upon exposure to rain or any other moisture source."
PS: It is not actually the sun that causes wood to warp per se, it is the rapid change in moisture content. The sunn exacerbates the problem by drying wood out quickly.