My thoughts on these 3:
Uno - the best of the lot with well presented buses, including using the right vehicle for the correct job. Now a massive rarity, articulated Citaros used on the Hatfield university area shuttle, double deckers on the routes that need them and mainly longer single deckers on all other routes. A nice mix of types for an enthusiast and plenty of heavyweight stuff instead of just E200s and Streetlites which are used in small quantities around Hatfield (more are used around Cranfield and Northampton). Friendly drivers who even informed me of their, at the time, brand new buses on the Dragonfly 610. Those really show how much thought has went into the investment of a key route - the use of a new design was risky (MCV eVora Volvo B8RLE) though the large windows give a great customer experience, combined with the natural cinematic seating that Volvos provide due to the large engine. Bespoke seating looks and is comfortable with use of USB Charging ports too. This is proved by them winning multiple awards in the most recent bus awards, the sort of operator that should be looked up to. I undertsnd more investment is on the way with 2014 air conditioned Volvo B7RLEs, formerly used in Malta, which are being branded for another route. Their fares seem a little high but at least it is being used for investment in new buses
Centrebus - the area where they compete with Arriva and Uno seems to be their best part. As previously mentioned, they are one of the few operators with 11.3m Enviro 200s (I approve

) and despite no brand new investment since those in 2015, they purchase some ex London 200s last year. Overall the fleet seems fairly modern though it’s a shame that when I visited, the oldest Scanias were employed on the busway whereas Arriva had 2011-2013 Volvos. I was told by someone their operations have been declining so it’s good to see they still purchased them E200s to renew the fleet. I understand Rail Replacements have become a major source too
Arriva - on paper they look pretty good but I noted plenty of Route branded buses off designated routes and allocations seemed fairly mixed. The fleet has plenty of modern vehicles with 2011-13 Volvo B7RLEs, 2014 Streetlites, 2017 E200MMCs alongside 2005/6 Scania L94UBs and when I visited last year, 2000 Dennis Tridents and slightly newer DAF DB250s. So in Luton they are pretty good and I didn’t have any bad experiences. However, in Stevenage, where they operate the routes into Hatfield, the trunk routes were using new livery E300s on a route that seemed to suffer majorly from delays. The Green Line 724 could do with a refresh, them 2006 Citraos must be rather life expired after so many years of express running. Subtle route branding is used on them, bringing back the Green Line livery would make a big impact.
For anyone interested in the length difference, I have attached a photo at St Albans of a Centrebus 11.3m vs a Metroline mini one. The slight editing probably helps, but look how shiny that Centrebus looks
