B&M.
People complain that they're too dependable, that their coasters are too smooth, that they don't take enough risks. I refute all that. We have the inverted, the A.I.Rs and the Dive Machines to thank them for - amongst others probably - floorless, maybe? Anyway.
You can depend on B&M to produce a top-quality coaster. They're smooth, and to me that is a quality, not something to criticise them for. If a rough coaster is thus described as having 'character', then I'd rather my coasters didn't have character. That can be made up for with theming/location/scenery.
Intamin have become very prominent. I have a few problems with Intamin - they're not terribly organised. They've known about a problem with Rita that is causing its downtime for several months now. The drum in the hydraulics shed needs replacing - years too early, btw - so Intamin are fabricating another one for free. Great, you'd think. However, they've not even fabricated the drum yet, with less than three months till the park opens. This may seem like a sufficient amount of time to make and ship the replacement drum, but actually removing the old drum and replacing it with the new is a huge operation in itself which requires the removal of the hydraulics shed roof.
I mentioned on TowersAlmanac that this was appalling - it's been known for months, Rita as a result has had to be removed from the Winter Weekends after her first season - and somebody defended Intamin saying they had two coasters on the go and they take priority.
My retort? B&M can have many coasters in the pipeline that need to be ready for a certain time of year, and they manage it. It was then admitted that Intamin are perhaps not as well-organised as B&M.
Also, their train designs. I hate having very little leg-room, I hate having to climb over, under, around the first seat and its open restraint to get to the second seat (i.e. with Rita, Collosus and probably Stealth too.)
And they didn't impress me with Rita this season, which has suffered downtime due to numerous problems including needing a new cable, broken restraints, unable to run in the rain (it's England??) and now the drum. There may be one or two other reasons.
Maurer Sohne impressed me with Spinball Whizzer and Dragon's Fury (although downtime due to misaligning bars and breaking excavation platforms wasn't great) and with G-Force at Drayton Manor (which I happen to think is a great little coaster). Good little company.
So B&M has to do it for me. Vekoma, unfortunately, I associate with roughness. Whether or not this assertion is completely fair, I couldn't comment - I haven't ridden enough of them.