I've always sent out C41, occasionally E6. For the latter it's a once every two years group development session at our photo club, and will perhaps do one towards summer.
Lab wise I thought that I managed to get unlucky even with real good prolabs with dip and dunk. In that case it was C41 but had some streaking in dense areas (sky) resembling bromide drag. Misscanned negatives, lost negative (once 3 years ago). Lost rolls in the post. A bit of everything. Sadly some of those were due to being very budget conscious during my student era, and sending out to other countries made sense.
The historically old chemistry issue IMO should be much less due to low turnovers nowadays as the "new gen" labs that are scan and mail based do a lot of work. In their defense, I'd say that they made film shooting much easier during the half decade they were established in the 2010s as they also sell film, making it easier to purchase and dev.
I developed my own film for a very long time, 60 years +, but color has gotten so expensive that on a fixed income for the few rolls I shoot every year I use a color lab. For the part for color I use on digital.
Anyways, as C41 goes, I tend to batch it and send out, to get it mailed back home or even picked up. I was having a conversation with another photo club member, and my set up made sense and was more economical that DIY if counting other factors (6€ a roll in Spain). I tend to also point that it's false economy trying to squeeze some simplified C41 chemistry rather than just paying a bit more for proper development.
Brand and type of equipment should make no difference to C41 processing. A lab is usually only as good as its owner/staff/operators.
foc did some of my film a decade ago before retirement and all good

As of E6, it's either big labs that still ahve the infrastructure, or many of the newer labs just run some batches on JOBOs. Chemistry age is more of a factor, last year I had a single E6 roll for a season so it was chucked with the C41 and the lab ran it in their batch. If anything, that E100 looked a bit dark and I wonder if it was 6 or 3 bath kits.
Also for the last 2 years, I've had a trip to Asia and developing it locally in at the end of the trip made it much more easy and convenient. I've got to meet some passionate people working their labs there and a bit of the local community that way.
B&W I always do myself.