[Ed. Note- An opinion piece that was objective enough for me to ask Greg if he wouldn't mind me posting it.]
Sorry for getting on this thread late. I've been away and am just catching up on mail. Erik began a healthy discussion and I know several people on the list have responded on this one. Since I own both a TR6 and an MGB and love both of them, I feel compelled to offer my hopefully unbiased experience/opinion.
The TR6 referred to below in Erik's test drive undoubtedly had some serious problems with the suspension and other areas (as a previous lister also pointed out). A stock US TR6 in good operating condition (up to factory specs) will out accelerate a stock MGB (pre or post 75 model) by approximately 2 seconds in a 0-60 run. Late single Stromberg MGB's are even slower. Having said that, the difference in displacement of the TR6's 2.5 liter vs the MGB's 1.8 liter SHOULD yeild a much greater power difference than it does. The fact that it doesn't is a disappointment.
The US TR6 is pretty well choked down to meet Federal emissions standards (by 1975 & 76, its was choked down to 7.75 compression making it a little slower than pre 75 TR6's). The stock UK TR6 screams with 152 hp while the US TR6 has only 106. The nice thing about the TR6 engine is that it is relatively easy to un-choke the US version to get about 145 to 150 hp without doing anything more than putting in a mildly uprated cam and bumping the compression ratio up to 9.5. If you want to go with webers and a header, there is even more gain. But the torque is what you really feel in the TR6. Even the stock US TR6 2.5 liter six has gobs of useful torque that make freeway cruising at speed a pleasure. I love the feel of cruising at a steady 70 mph and then punching the accelerator and feeling it pull smoothly upward to 85, 90 and beyond. My 68 MGB beats my brains out driving at 70 mph. Definitely not a pleasure on the highway. (I'm comparing both without overdrive. Apples to apples.) The place where the TR6 wins hands down is just the smooth torquey power curve of its engine (even choked down to US specs). It just feels like it will keep pulling endlessly and does it very smoothly.
Now lets talk handling. I'd say the MGB edges out the TR6 in tight, fast cornering. The TR6 handles fairly well with one major caveat. The TR6 is nose heavy and understeers unless some suspension modification is done to correct it. The MGB feels more balanced in corners and seems to corner a little better (again, comparing stock specs to stock specs). But by no means does the TR6 six handle like an El Dorado or "rock like a boat" unless something is very wrong (remember, just like old MG's, there are a lot of tired, worn out TR6's out there that people don't take care of). I guess I'd say that on a flat, smooth, tight autocross course, assuming the tires of both cars have equal stickiness, I think the stock MGB would out corner the stock TR6. However, on a decent sized ROAD course where I had to accelerate to the next corner ahead of my competitor, I'll take the TR6 and just manage the understeer. And don't underestimate the TR6's independent rear end. All things being equal (ie, up to spec: bushings, shocks, and springs not worn out), the TR6's rear end grips uneven road surfaces extremely well compared to a live axle. Now, I'll be the first to admit that it does not have the range of travel and is not on par with a really well engineered independent rear end like a Vette. It was a typically cheap BL compromise. But its decent.
In terms of creature comforts, I'd say my MGB is more comfortable to sit in. The passenger compartment is several inches wider than the TR6 and that extra elbow room makes a real difference to me. The TR6 has a little more leg room just because it is longer, but the leg room doesn't overcome the confined feeling of your elbows pinned at your sides due to the lack of width. I can't really address the dash or seats since, at least on MGB's, these continued being revised through the years and it is somewhat subjective anyway. For example, I hate the fact that my 68 MGB has no glovebox. But I will say that, IMHO I think the TR6 dash is a work of art. That, I'll admit is subjective.
The rest of the criteria is also mostly subjective opinion (body style, reliability, etc) so I won't even talk about it. The bottom line for me is that they are both wonderful cars that I dearly love. But like my children, I love them each for their different positive qualities and try to work around their negative qualities. BTW, I do sometimes find it amusing that some listers are reluctant to even spell out the name Triumph on this list. Like they're afraid of being ostracized. :-) Its like the Chevy vs Ford good old boy rivalry. Interestingly enough, I'm on both mailing lists and I've not really noticed as much reluctance to mention MG's on the Triumph list (some of the people on the Triumph list also have MG's). Just an observation.
Regards, Greg H. (both Triumph and MG enthusiast and hopefully, one day, Jaguar enthusiast, too)
I could have elaborated a little more on how much more of committment (parts and labor) renewing the TR6's rear suspension is (diff mounts, rear hub bearings, u-joints, and bushings) once everything wears out. I suppose that is a negative on the TR6 compared to the simplicity of the MGB's rear suspension which, even when its worn out, doesn't have near as dramatic of an impact on the way the MGB drives. When the TR6's rear suspension is up to specs, it can't be beat. But when its shot and worn out after 100K miles, its a BIG and potentially expensive project. And, if the owner keeps driving a TR6 with a badly worn out rear suspension, it can cause damage to more expensive components. I know. I've had to do the whole thing before! But, that's typical of ANY independent rear end (Jaguar, etc). With the MGB, if the rear suspension wears out, for the most part, you just have a softer, bouncier ride, but it'll keep on going with out ripping part of the frame out like the TR6 will in extreme cases of abuse!