The shub 2 was a massive improvement over the shub 1 but that being said it is antiquated technology and things have moved on big time in terms of wifi standards. Generally speaking the shubs are pants because they are made as cheap as chips and VM don't want them to have too many features a) because of cost and b) in terms of support. I would recommend taking the shub 5 over the shub 2 but that being said, if there is any aspect of the performance you aren't happy with, the best thing you can do is put it in modem mode and buy your own proper router.
Here is some food for thought in the way of friendly advice. Wifi and wireless devices are becoming less of a novelty and more of an essential. Just on wifi in my house I have got laptops, tablets, mobile phones, Sky boxes, Amazon Echoes and lights. At any one point in time somebody is streaming video, music or doing something else. When you do that you don't want wifi that will "hopefully work" and "may be fast enough". You want to have the technology and network infrastructure in place to facilitate the seamless use of those devices. In the evening when you get home from work you want the lights on, heating, tv, oven to make dinner etc and you don't cross your fingers and hope the power supply in the house holds out; you expect it.
Get the shub 5 and see how it goes and if it doesn't meet your needs have a quick browse at this
thread and consider your options and how you would to proceed going forward. To put things in perspective for you, there have been thousands of posts in this forum over the last 15 years with people complaining about wifi coverage in their houses. From day 1 when I got broadband back in 2001 I have had my own router and over the last 21 years I have never had any reason to complain about any aspect of my network performance because I have always had a proper router, proper switches and good quality cabling. The irony is that there have only been two times I have complained about major issues with my internet connection and loss of connectivity and on both occasions it was because VM screwed me over with new shubs that I didn't want and they were both broken.