I have experience with several boxes. I have a Zgemma H2H with virmen in the family room. a zgemma hth running sly in our bedroom and in the study i have a roku box running plex server, a mag 254 a android box running a few apk's and a zgemma i55 box.
the differences between the mag 254 and zgemma i55 are mainly in the user interface. Using iptv i find the mag and i55 both have the same amount of stability. I love the i55 as i have it set up exactly the same way as my H2H box running wooshbuild. its slick and pro looking. the 254 is very basic, but basic works without a hitch.
ive found it difficult to get a decent set up on the i55 as not alot of providers cater for the boxes. but i have recently taken out a sub and have been blown away by it. not only has all the channels been split into appropriate bouquets but there is a fully working epg and also allows you to record.
The only thing i noticed is the vod feature with the mag254 works better than on the i55.
it will ultimately come down to personal preference i love the way the i55 works at the moment looks top notch. but the simplicity of the mag will be appealing to others.
The zgemma h2h can run iptv but it struggles with some of the FHD channels taking a little longer to load.