You really can't compare October to April. Yes, they are both "off season" but in October most of the mountain cable cars, hiking paths, etc. are still open, so almost everything is still accessible, just quieter. In mid April it's a different story. Ski season has ended, but weather can be a mix of snow, slush, rain, etc. making for messy hiking and very few of the main attractions will be open. Unless your vision of your trip is to simply go to Jungfraujoch, walk around the town, walk around in the Lauterbrunnen Valley and maybe go to the lakes, I think you might be a bit disappointed with the weather and available activities. Personally I'd only go to Wengen in ski season or mid June to mid October for mountain activities that don't involve skiing. November and April are when locals take their breaks from the busy summer and ski seasons and do a lot of maintenance to transition seasons. If mid April is your only option then you might want to consider staying on the lakes at lower altitude and taking a day trip up into the mountains on a decent weather day.