Well, I've tried both of the Pentaxes, Gossen, Minolta, Soligor and SEI.
I'd back Minolta as the easiest and quickest, but unfortunately mine broke and besides Minolta is no longer in the business.
The Pentax V is huge and heavy and takes hard-to-find batteries. But it's well made and easy to use. The Zone VI modification is great if you believe in fairies at the bottom of the garden. I have an unmodified one.
The digital-readout Pentax is a LOT smaller but still wants an odd battery. It's my wife's standard spot meter.
The Gossen is pretty good but the viewfinder is small, the controls are not intuitive and Zone provisions are downright weird. It's also bulky but at least it uses a readily obtainable 9v battery. I have one and can never decide between it and the big Pentax.
The Soligor is cheap and cheerful but not as well made as the others and it's worth checking (with a candle flame) that the one-degree spot actually coincides with the circle in the rangefinder. On the one I borrowed, as far as I recall, it was offset about 1/4 decree to the lower right -- but it was a long tine ago. Actually, this check is worth carrying out with any spot meter.
The SEI is a brilliant piece of engineering and can read 1/2 degree or less but you really need Huw's LED conversion, so it's a bloody expensive option. The upside-down viewfinder is hard to get used to, too. I have one.
Cameras with built in 'spotmeters' are no substitute. Quite apart from being bulky and inconvenient when used as meters for another camera, the spot size is normally too big to be really useful.
Nor can you substitute 'spot attachments' for other meters unless they give you true 1 degree metering. Yes, a 5 degree 'spot' is better than nothing (I have the attachment for my Gossens) but it's inconvenient and less informative.
Hope this helps
Cheers,
Roger