Now, while I respect Greg's opinion and experience, I have relied on Aristo screwed fishplates for 10 years - two different railroads in different gardens, but the same track.
It's a funny old thing, and they probably (almost definitely) wouldn't work for the sort of current that Greg uses on his 5-loco lash-ups, but for ordinary DC operation with low current draw locos (I frequently double head a pair of Bachmann Connies) I've found them to be OK.
I use clamps for LGB track but have used the screwed fishplates even for connecting Aristo to LGB (I bought quite a lot of second hand LGB flexi) which is not entirely straightforward as the rail profile is slightly different on the bottom flange - right where you want to put a rail joiner
But, at the same time, I am an expert in cheap