I dont have my own servers, but for my PC and Monitor it is Dell all the way.
19 years ago i got a Patriot PC from a well know retailer in the UK, in 12 months i had engineers out almost monthly due to issues, so in the end they refunded me along with some compo, so i decided to go online any order a PC from Dell as you could configure to suit your needs. This PC lasted me 10 years before it was uneconomical to upgrade further, so went back to Dell for a replacement which i got in 2008. only issue was 3 years ago i had to replace the power switch, but recently its need to be booted 3 to 4 times to bring up the login page, so i have just ordered another PC again from Dell ( only thing i noticed is you dont get to configure them as much now), but i dare say this one will last another 8 years at least.
we found the exact opposite, DELL enterprise DRAC cards are very easy to use and have a lot more features than the Supermicro IPMI.
HP are realiable as well, but they charge a yearly fee for the iLO cards
we have had supermicro and customers with colo used supermicro and seen lots of problems.
The issue is in Canada is that supermicro are basically custom builds so it can very from dealer in terms of support, etc.
we standardized on DELL servers and we have a DELL reseller/ dealer 15 min from our office with over 1000 servers in stock at any given time. IT helps us with parts, replacements, new servers, etc ...