I purchased an economy casual kilt last summer from Scotweb in mediumweight 13 oz wool and have worn it often. It inspired me to try my own hand at kiltmaking. I have made a casual knife pleated 5 yd kilt in 16 oz Black Watch for a student and he wears it throughout the year. Injust finished one for myself in 13oz messy Spirit of Scotland that I really love and expect to wear frequently. Have worn my 16oz Royal Stewart box pleated throughout the year since I finished that last fall as well, and it is comfortable. In my limited experience, box pleaters are comfy anytime in med or heavyweight wool, casuals are best in med weight, and my 8 harder has been most comfortable in cooler seasons (it is 16oz Isle of Skye).
Those are the recommendations I have been giving to area folks who want me to make them a kilt (dedicated amateur style).
Harvey