My opinion is a LG Nexus 5 is still a reasonable specced device, in fact it has a better/faster processor Snapdragon 800, main thing is it doesn't have SD, if you want to store lots of multimedia.
However something you might very well notice with the TCL/Alcatel, is a heavily customized and skinned version of Android, while the Nexus is a pure Google experience. Also updates, a Nexus is updated promptly by Google, Chinese phones frequently are not, and may never receive any Android updates at all, like the forthcoming Android M.
That did make think me think about the lagging you mentioned after a month, was that reported somewhere with this TCL/Alcatel phone? Certain Chinese versions of Android have been known to be buggy before now, e.g. Oppo's ColorOS 1.0 versions, and some can be rather bloated as well.