keeping in mind the compared products
I've just gone from a 42" tv through vga/hdmi to the samsung s23a750d and the difference is night and day. Far more than it would ever have believed.
Here's a simple comparison of size:
http://displaywars.com/23-inch-16x9-vs-42-inch-16x9
Assuming your TV has a maximum resolution of 1920x1080, which is the same as what the S23A750D offers, it's fairly safe to say it can't offer the same sharpness...
Now, I don't know which model your 42" TV is, but I'm willing to guess it doesn't offer 4:4:4 sumsampling. Furthermore, I hope the VGA you mentioned wasn't actually in use, because that usually gives an undesired blurriness. And I hope it's at least Full-HD, not just HD-Ready.
But in any case, anyone reading this should keep in mind that some TVs are more suited to PC use than others. You can't just buy ANY television, you should always ask for recommendations in the forums (like this one). And if the TV will be standing on your desktop, you really shouldn't go much higher than 32".
PS. With "PC use", I'm talking about using the TV as the primary display for the computer. If using the TV as an occasional companion for movie watching, etc., the requirements are much lower. Pretty much every modern TV is good enough for that.
PS2. Getting a TV as a primary PC monitor is not for the faint of heart. There are usually compromises you will have to make.