Hi there, I use autocomplete extensively and currently have 3 different ones going while I decide which to stick with! All are the "free" versions, if commercial versions often have more features.

SpeedTyping - started with this one. very good, very quick, can get it to replace with or without the space added afterwards. Limitations - free version does not allow grouping or rearranging the phrases so once you have a lot it is difficult to find them if you forget the shortcut keys! (which I frequently do). Does not allow spaces in the shortcut phrases. Few options.

Autohotkeys - Very useful and multifunctional. Can cope with spaces in the shortcuts. slower than phrase express. But can have one file with several different scripts in it (using less resources but some bits then stop working as I have little script writing knowledge). The challenge is how to keep track of an ever increasing list of short cuts - any ideas welcomed.

PhraseExpress - very useful as you can organise your phrases into sections making it easier to find ones and edit them plus the shortcut keys to bring up the list so you can just choose the one you want.

The challenge: how to remember all of them!
Have started using the opening word or letters and adding one of the letters till it makes a combination that is NOT part of a normal word (or you end up with it autocompleting things you do not want) eg

hr has a shortcut of   hh
hr class="b" has a shortcut of   hhb
or pick a letter nearby that is never a complete proper word -
title=  uses the shortcut of   ttt  (as tt occurs in too many words)
this is a recent scheme and seems much more reliable than my others!

The whole idea of autotext is to reduce the amount of typing and finger movement (especially as I have arthritis) so it makes sense to use keys close to each other and easy to use for your shortcuts.
I would welcome other tips on how to device memorable shortcuts!