They are very different. Liz is an shitty friend to both Asuna and Kirito and has more similarities with Inoda in her personality. She wants to fuck Kirito, there are no feelings, maybe a crush of sorts at best, unlike Suguha who is concerned about his well being. Don't get me wrong, she is not an good person, as she basically rapes him. Also another big difference is that Sugu doesn't care for his size or performance, she made this clear on several accasions, unlike Liz who right at the first interaction admited that Inoda is superior. Liz is also pathetic, she isn't confident, and can't do anything by herself, that why she needs to prepare with Inoda before approaching Kirito and that why she will fail and fall.