Sorry for the delay, I became distracted and forgot.

Yes, clients = different programs.

A client developer would be the best one to point these questions to.

1. I suspect all clients are about the same in the regard of search horizon. This is due to the way the gnutella protocol was designed. The later developed clients incorporated the ability to search outside the immediate horizon. This would include LimeWire clones, Phex, GTK-Gnutella. Not sure about ShareAza because it only has a basic gnutella ability which has not been upgraded very often in the past several years. BearShare 5 I am also not sure about, it was an advanced client during its days. But that was 6 years ago before BearShare was sold and moved to a different network (a semi-commercial network under the RIAA's indirect control.)

2. Questions 2 and 3 are very similar.
I suspect most clients are similar in that they attempt to connect to what were the known peers who had the file at the time the file was initially downloaded. If those persons are not online then ...or if they are too busy uploading to others ... and that's usually a huge part of the problem.

If you are referring to an auto-search function. I am not sure if any client has this ability. I recall in the very early days of the network, one client had a similar ability but was put into line by the other gnutella developers due to the massive network traffic it was causing with its behaviour. Even the attempt to auto-connect to the hosts of the incomplete downloads is only done in intervals of every 30-60 minutes. LW and Phex do this. Again, not sure about the other clients.

4. As previously mentioned, I suspect a few clients have the ability to 'save' search terms between sessions, but I am not sure about search results. I might be wrong but I thought Phex had something almost close to what you mean. But I confess I have not used Phex for searching and downloading since early in the year. Only times I've had Phex open since I was simply sharing files.

5. What you experienced with LW 4.18 I have not seen happen. Unless I misunderstood the situation where you were unable to scroll to the bottom of the search results. That seems odd. I am wondering that if you had have temporarily stretched the program's dimensions lower and wider a little bit, if that might have overcome that quirky behaviour. The only other thing I can think of is the search results at the lowest part were auto-designated as spam, and you have LW's settings set to hide spam from search results.

I do not think I really answered your questions well. But I do have limited knowledge. To look for the 'ideal' client. I think each client has things that are better than the others or the others do not have, but there seems to be none that have the best of them combined into one.

For example, I like how BearShare 5 shows how many shares and what approximate total file size of shares of the peers it's connected to. Phex also has this ability, though I suspect BS is more aggressive about obtaining the information. The history of searches, something I think both GTK and Phex have can be handy. Phex keeps a history of your uploads. I liked the direct connect tool and the advanced file description tools of LW 4. I like LW's drag and drop option for adding files or folders to shares which seems to be an ability other clients do not seem to possess. There will be other things I like about particular clients but cannot think of them at the moment.