The decision is up to you and your needs.
LR 6.4 the latest version costs. $149. Upgrades which will have new advanced features will need to be done approx every 18 mths when you check the history of Lightroom.
Adobe also offers the Photographers plan which offers Photoshop CC 2015 and includes Lightroom CC 2015. for $9.99 per month( The price in your country of residence may vary). Lightroom CC will add new features as it gets updated approx every three months, at present LR CC has a couple of new features that are not available in LR 6.4 like debase.
LR CC also has the ability to sync your photo's via the Creative Cloud with your mobile devices i.e. iPad,Adroid Tablets, iPhone and other Smart Phones. LR 6.4 will not offer these this feature. Photoshop CC is the priemer software application offered by Adobe for editing image files and has many more advanced features than Lightroom. To wit Lightroom is not an alternative to Photoshop.
There are two issues that you have to consider.
1.How long will Adobe continue to upgrade Lightroom as a standalone version. They have stated a little over a year ago that they will continue to do so for the foreseeable future.
2. How long will the $9.99 per month price be maintained.
At the present time the monthly subscription is a great offer for Photoshop alone and you get Lightroom CC as a bonus.
Only you can decide which is the better deal for you.
$10 per month is a great deal for Lightroom and Photoshop.