It really depends on the TV. You can buy those Electrohome 25" tubes (that have SVIDEO in, btw) that are absolutely PUTRID in quality (but cost only 3/5 of any other brand).
I think there's a major OEM that's made a bunch of low-cost 25" tubes that all those offbrand companies buy.
27s seem, on the other hand, to be large steps up in overall quality - but you can't buy them without paying for the extra stuff you'll never use (stereo, Guide+, etc, etc).
As always, YMMV - and I can only speak to the Canadian market, not the American.