I'm going to Northern Finland/Sweden in March and will be walking up to 20 miles per day in temps that may be -20 or lower. I've used pac boots before but find them to be a pain to walk in. I'm not too fond of my Lundhags either. I've got insulated climbing boots but they're not great to walk in. I'm currently thinking of using Scarpa Mantas and insulated gaiters. Are there any better options?
In reply to Flatus Vetus: If it's only snowshoeing, I'd get some comfy, light snowboots of some sort. Plenty of firms like Jack Wolfskin, TNF, Columbia, Salomon etc. make them. They have a pretty flexi sole and often the shoe section is one piece rubber which is useful if it gets slushy. Probably something with a pull out liner to help you dry them at night. Sorrels are the classic, but there are plenty of more modern designs around. In March it's very unlikely that daytime temperatures will be that cold. It's possible, but rather unlikely. Any boot with a flexi sole and then walking will keep your feet way warmer than a climbing boot does. I happily wear some light fabric Merrel hiking boots for a lot of my winter snow shoeing. Some people I know just wear running shoes.
Are you camping? Staying in huts? Pulling a pulk? All of that will make a difference.
Finally, why snowshoes not skis? March in Lapland is prime ski season. There are many hundreds of kms of prepared tracks, thousands of kms of tracks left by other people hut to hut or camp touring, and you can make your own tracks of course as well. I've tried snowshoeing in Lapland at that time of year, and even with huge snowshoes breaking trail was completely exhausting. We didn't reach the potential icefall that we wanted to see. Even just track skis would have been a lot better, let alone proper touring skis.